TAMPA, Fla. — Did you hear about the women who hid all night underneath the truck?

Rumors were flying outside the Raymond James Stadium more than 36 hours before Taylor Swift took the stage of the 75,000-seat site on Florida’s west coast.

They went from person to person, as in a children’s game of telephone. But the lines outside the stadium last week were made up of fans of all ages willing to put up with hours of discomfort to buy souvenirs tied to the singer’s Eras Tour. Many of them arrived well before sunrise.

When word went out that certain prize items might be sold out, some Swifties spoke darkly of resellers with suitcases who had bought up boxes of T-shirts and sweatshirts at previous tour stops. There was also talk that a couple of women had spent the night beneath a merchandise truck.

That turned out to be true. One of the women, Larisa Roberts, had the selfies to prove it — grainy photos showing that she and a friend had spent hours taking shelter from the rain under the official Eras truck.

“No one was here,” Ms. Roberts, an interior decorator from Trinity, Fla., said of the scene outside the stadium when she arrived between 2 a.m. and 3 a.m. on Wednesday. She added that she planned to buy sweatshirts for her daughters, Lilly and Daisy.

Shirley Vogler, a nurse in Tampa, said she had made it to the Eras truck at 10 p.m. the night before. Like other early arrivals, she had been moved from spot to spot by security guards in the rainy predawn hours. At 5:45 a.m., she was among the hundreds of people camped out on a sidewalk next to the six-lane West Dr. Martin Luther King Jr. Boulevard. Ms. Vogler, 31, was seated on the ground toward the front, chatting with two other women whom she had befriended.

Fans were able to buy merchandise inside the stadium on each of the three nights that Ms. Swift would perform at the home of the Tampa Bay Buccaneers. So why bother waiting all night in the rain? Ms. Vogler, who had tickets to a show, said it was because of what she had seen on social media — specifically, “the TikToks about how bad all of the arenas are with the merch lines and the traffic.”

Several other fans mentioned having seen posts by Bailey McKnight-Howard, one half of the twin influencer duo @brooklynandbailey, an Instagram account with nearly nine million followers. A few days earlier, Ms. McKnight-Howard had put up pictures of herself waiting outside AT&T Stadium in Arlington, Texas.

She had also modeled a newly purchased blue crew neck sweatshirt, the most-sought after item among fans. Nearly every person outside the stadium on Wednesday morning was trying to buy one, or two, or as many as they were allowed to have.

There was nothing flashy about it. The sweatshirt had no sequins or embroidery or hidden pockets. It was just your average everyday sweatshirt, with Ms. Swift’s name and “Eras Tour” printed across the front and the tour dates and the titles of her albums on the back. If you closed your eyes and conjured a blue crew neck sweatshirt with some writing on it, your mental image would probably match up with this in-demand item.

One thing that made it special was the fact that, unlike some other tour souvenirs, it was not available in the “merch” section of taylorswift.com. It was also, notably, the rare garment for sale that day without Ms. Swift’s face printed on it. In the weeks since the start of the Eras Tour, fans had elevated this unexceptional article of clothing to cult status.

“Every Swiftie wants the blue crew,” said Debbie Losee, a 60-year-old teacher who said she was waiting in line on behalf of her daughter.

The apparently limited supply made it even more prized. “The resale on the sweatshirts is $300, Jake!” one fan was heard shouting into her phone. She was correct. The sweatshirt is available on eBay for more than four times its $65 list price.

“I’ve been having nightmares about getting this crew neck,” said Emily Rottkamp, a 20-year-old employee at Disney World. “I haven’t been sleeping.”

Alyssa Misay, a personal injury specialist from Land O’ Lakes, Fla., joined the line before 5:30 a.m. She said her teenage niece had given her strict instructions: “‘The sweatshirt, the sweatshirt!’”

“Social media just makes things a bigger deal than what they are — like, almost unattainable,” Ms. Misay, 36, said. “Like, if you don’t have it, you’re not cool in school.”

Nearby, Venisha Jardin, a sophomore at Wiregrass Ranch High School in Wesley Chapel, Fla., wore a hooded plastic poncho to protect her from the rain. In the hours before sunrise, the glow from her phone illuminated the area around her. “I’m missing school for this,” she said.

Her mother, Chrys, was sitting in a nearby parked car.

“I was like, ‘There’s no way I’m missing merch just to go to school,’” Ms. Jardin said, describing how she had managed to convince her parents. She added that she planned to buy at least five items, including the you know what.

Despite the chill in the air and the steady drizzle, spirits were high. Gina Delano, 27, walked up and down the sidewalk telling people she had a cooler full of free snacks and drinks. Wearing a cardigan that had gone on sale at taylorswift.com at the time of the singer’s 2020 album “Folklore” (which includes the song “Cardigan”), Ms. Delano said she had traveled from her home near Buffalo.

“The weather could definitely be better,” she said, “but if this is what it takes to get merch, then this is what we’ll do.”

Elsewhere in the line, Jess Montgomery, a wedding photographer from Dade City, Fla., cradled her 7-week-old son, Denver, in a blanket. Standing beside her was her 11-year-old niece. “I’ll be 40 next year,” Ms. Montgomery said, “and when she’s my age I want her to look back and say, ‘My aunt was super cool.’” She added that she had struck out in her attempts to score tickets for any of the three sold-out Tampa shows.

The people outside the stadium included teenagers who had never known a world in which Ms. Swift wasn’t an international superstar and women who had grown up alongside the 33-year-old singer. The hours of waiting gave them a chance to feel at home among hundreds of others who shared a love for Ms. Swift’s songs about high school bullies and first loves, about heartbreak and loss.

“The worst kind of person is someone who makes someone feel bad, dumb or stupid for being excited about something,” Ms. Swift said in a 2019 interview. It’s a line that her fans have often quoted on social media in reply to the haters.

Shortly after 7 a.m., Matt Langel, a Tampa resident, was sitting on the sidewalk decked out in Pittsburgh Steelers gear while his daughter, Alexis, filmed the scene for her mother. Ms. Swift’s music had become a lifeline for the family, Mr. Langel said, adding that his wife was disabled. “My wife, since she’s been bedridden, pretty much Taylor is what got her through,” Mr. Langel said.

At 8 a.m., two hours before the merchandise was to go on sale, stadium workers opened the parking lot. Some fans tried to respect the existing line as others rushed toward the front. Because many people had been waiting at different locations, there was a scramble. Fans who tried to abide by an honor system found themselves more or less out of luck.

“Everyone started running from all different directions,” Ms. Roberts, the woman from under the truck, said after she had managed to secure a spot near the front of the line.

Farther back, some people squabbled with those trying to cut in. “Back of the line or I’m going to have to put you in jail,” an officer with the Tampa Police Department can be heard saying in a video of the scene recorded by a fan and reviewed by The New York Times. Some people cheered as several of the apparent line-cutters obeyed his order.

As 10 a.m. approached, local TV news crews showed up to interview fans, and a helicopter whirred not far above the merch truck. Strong winds whipped across the lot, stirring up dust. Tears streamed down Haylee Lewis’s face.

“I just feel like camping overnight is a little much,” said Ms. Lewis, a 21-year-old college student who lives in Orlando. The line was already over 1,000 people long when she had arrived at 8:30 a.m., she added. “I understand it, maybe, for concert tickets, but for the merch line it’s actually insane,” she said.

There turned out to be two trucks selling merchandise. Next to the Eras truck, which was patterned with images of Ms. Swift’s face, there was a plain black truck topped with a sign reading “COOL STUFF” in big red letters. Both trucks sold the same items.

Inside the trucks, sales people prepared for the rush, unpacking boxes of shirts, tote bags, light wands and posters. They wore black Eras Tour T-shirts, the same ones they would be selling for $45 apiece. (Online, some fans have complained that certain shirts fade noticeably after washing.) There was one rule for the day: only two blue crew neck sweatshirts per customer.

At 10 a.m., the line lurched forward. A pair of AirPods flew into the air and landed on the ground, their owner seemingly oblivious. Things progressed slowly as the fans who made it to the very front asked to see various sizes and mulled their options. The mood was tense but jovial.

Less than an hour later, the vibe shifted as word circulated that the prize sweatshirts had sold out. Anna Avgoustis, a 26-year-old fan, got one of the last ones.

“By the time I got to the front, they were taking them off the wall,” she said. “I was like: ‘Please give me the last one. I will do anything for you. I’ll run you guys Starbucks.’” A few hours later, true to her word, she returned with coffees for the sales crew.

Kristi Kall, 38, and her daughter, Kaylee, 11, said they would try to buy a sweatshirt at the concert. “I just wish they would have had a little bit more, because they knew that’s what everybody wanted,” Ms. Kall said.

“I’m a little upset,” said Kaylee, who bought an Eras Tour-branded water bottle instead.

In the afternoon, Laura Gavagan, a 33-year-old fan in Baltimore who had come directly from the airport, joined the line outside the truck, her suitcase rolling behind her. “I’m getting some looks,” she said.

Jaclyn Quinn, a high school English teacher from Joliet, Ill., said that Ms. Swift’s work came in handy in her lessons. “We use ‘The Man’ to teach critical lenses and talk about the feminist lens versus the genderqueer lens,” she said. “We use her song ‘Bad Blood’ to talk about metaphor.” She bought an Eras Tour wall tapestry for her classroom.

As 5 p.m. approached, the salespeople began straightening up the trucks and peeling off the tour T-shirts. When asked if they got to keep the shirts they had worn that day, one of the workers said, “No.” Instead, they folded them and returned them to the stacks to be sold to the next day’s fans.

“Isn’t that so gross?” the salesperson said. “Don’t tell.”