Bigfoot Is Back. (Bigfoot Never Left.)

Stetson Parker and his wife, Shannon, recently took a trip through Colorado to celebrate their 10th anniversary. They boarded the Durango & Silverton Narrow Gauge Railroad, a vintage train that “provides historic and entertaining” rides, according to its website.

But what the Parkers saw from the last car of that train wasn’t advertised online. The couple believe they spotted the most elusive of creatures: Bigfoot.

Yes, you read that correctly: Bigfoot. Also known as a sasquatch or a yeti. The mythical apelike, giant creature, who (maybe) wanders North America. Who, according to some, definitely exists. And who, according to most everyone else, definitely does not.

The most recent spotting, captured in a widely shared video from that train in Colorado, adds to the growing catalog of sightings that have kept the myth alive amid a lack of what some might call verifiable proof.

“I’m definitely a believer now,” Mr. Parker, 33, said.

The video, which was taken by a fellow passenger and posted online by Mr. Parker, shows a tall, brownish creature walking and squatting, before it blends into its surroundings. The footage is zoomed in, making for a grainy video.

To him, Mr. Parker said, the creature didn’t look like a human.

“It didn’t move like a person,” he said. “It looked more like an ape but didn’t walk like an ape so much.” He added that the creature’s arms seemed too long to be human, with hands reaching down to its knees.

“It didn’t look like anything I’ve ever seen before,” Mr. Parker said. “I don’t think it was a hoax. And if it was, it was a really good one.”

Other possible explanations emerged as the video drew the attention of media around the world. Maybe it was a bear. Or, the most common one, maybe it was a man wearing a ghillie suit, the camouflage clothing that helps outdoorsmen disappear into their backgrounds. But why, Mr. Parker asked, would anyone be in a ghillie suit in the middle of elk hunting season? That’s a surefire way for any hunter to get shot. And it wasn’t holding a weapon.

Over the decades, researchers, academics and even the F.B.I. have investigated Bigfoot’s existence. The F.B.I. helped research mysterious hairs in 1977, which ended up being of deer origin. Bigfoot experts and enthusiasts often refer to the so-called Patterson-Gimlin film from 1967, which claimed to show one of the creatures strolling through a California streambed.

A major 2014 Oxford University study dealt a blow to Bigfoot believers. Researchers there investigated 30 hair samples and successfully matched all of them to other animals.

But the Bigfoot faithful are not easily deterred. “I fully believe that they’re there,” said Ryan Willis, 23, who founded the Trent University Sasquatch Society and is the host of “Sasquatch University,” a reality show on the Wild network that covers Bigfoot sightings in Ontario. “But I do leave a bit of room for skepticism.”

Mr. Willis said people had sent him video footage, hair samples and more. In some cases, he said, people have told him they have fecal evidence. But, he said, “Nobody has sent us Bigfoot poop in the mail or anything.”

Even Bigfoot believers disagree over what the video shared by Mr. Parker shows.

Cliff Barackman presented the reality show “Finding Bigfoot” for nine years on Animal Planet, and he opened the North American Bigfoot Center in Boring, Ore., in 2019. He doesn’t think it’s Bigfoot.

“I thought it was a suit,” Mr. Barackman said. “I have seen a sasquatch, and I know they are real animals.” But the creature in this video, he added, “didn’t look like it was an animal, it looked baggy.”

But what kind of suit is unclear. Most online viewers suggested it was a ghillie suit, which usually includes a jacket, pants and a head covering and is supposed to camouflage any human form. Kevin Erickson, the chief executive of Arcturus, a company that makes the suits, said that the creature in the video was not wearing one: The suit wasn’t baggy enough.

“In this video the extremities — the legs and arms — are fairly silhouetted and tight,” he said. “No one makes a ghillie suit like this.”

But, Mr. Erickson added, it could be a “Bigfoot-specific suit.” Upon close inspection of the video, he said, he seemed to see a shadow in the middle of the creature, suggesting a jacket.

Skepticism is often warranted, Mr. Barackman acknowledged, because the internet is full of hoaxes and misinformation. And until Bigfoot’s existence is conclusively proven, he says he’ll continue to run his museum and search for the creature. But, he wonders: “After the species is proven to be real, are people still going to dress up as Bigfoot?”