As mysterious as its discovery, the strange shiny monolith that was found in a remote US desert last week has disappeared.
Photos from the area over the weekend show a pile of rocks and the triangular top of the three-metre structure.
One disappointed traveller wrote on Instagram: "After traveling four hours in the car, hiking 9 miles with over 2000 feet of elevation, I arrived at the Utah Monolith! You can imagine my disappointment when I saw that the aliens had come under the cloak of darkness eight hours earlier to take the Monolith home."
Officials at Utah's federal Bureau of Land Management denied they had anything to do with the disappearance.
It was the bureau's workers who first stumbled upon the monolith.
The structure was discovered by the Utah Division of Wildlife Resources in Red Rock Country while they were counting big horn sheep in a portion of southeastern Utah.
Immediately it was compared to the alien structure in the epic film 2001: A Space Odyssey.
Officials said it was not clear who created it, but warned that it is illegal to install "structures or art without authorisation on federally managed public lands, no matter what planet you're from".
Despite trying to keep the location a secret to stop curious hikers, the exact coordinates were posted on the internet.
David Surber, a 33-year-old former US Army infantry officer from Utah, told the BBC that he drove for six hours at night in search of the monolith after seeing a Reddit post that claimed to have pinpointed the location.
"I decided to go there first because I was drawn to the fact that this object had been there for five years, hidden in nature," he said.
Tim Slane, the Reddit user who shared the coordinates, said he had tracked the flight path of the authorities' helicopter until it went off-radar.
Suber said in an Instagram post that he had the monolith to himself for about 10 minutes before other people started to show up.
While it's still a mystery who installed the structure, experts believe it is a conceptual artwork, according to the BBC report.