In a nutshell: The mystery of the monolith recently discovered in the Utah desert has deepened after the structure disappeared---though there are some clues as to what happened.

On November 18, the Utah Department of Public Safety's (DPS) Aero Bureau, working with the Utah Division of Wildlife Resources, found "a metal monolith installed in the ground in a remote area of red rock" during a count of bighorn sheep.

Measuring between 10 and 12 feet tall, it's unknown who made the structure, how it got there, and the length of time it had been in place, though internet detectives used Google Maps to show it appeared sometime between August 2015 and October 2016. Many believe it to be the work of minimalist artist John McCracken, who died in 2011, or perhaps a tribute to him by a fellow artist.

While the appearance of a monolith straight from 2001: A Space Odyssey generated a lot of excitement, the DPS didn't appreciate the joke/tribute/promotion/alien message. "It is illegal, destructive to the rock, and potentially disruptive to the Big Horn Sheep if it becomes a trend," the agency said.

The location of the monolith wasn't shared publicly in case people got lost in the area while trying to locate it. That didn't stop visitors, of course, some of whom posted photos of the structure on social media.

As reported by The Guardian, Riccardo Marino and Sierra Van Meter visited the spot late Friday night to take some photographs. "All that was left in its place was a message written in the dirt that said 'bye bitch' with a fresh pee stain right next to it," Marino posted to Instagram. "Someone had just stolen the statue, and we were the first to arrive at the scene."

Marino said the pair passed a pickup truck carrying a large object driving in the opposite direction as they traveled to the site. A Reddit user, meanwhile, also posted a picture of the former site.

The Utah Bureau of Land Management (BLM) has denied removing the structure. "The BLM did not remove the structure which is considered private property," the agency wrote on its Facebook page. "We do not investigate crimes involving private property which are handled by the local sheriff's office."

Not every part of the monolith was taken. The perpetrators left behind the metal plate that sat atop the structure.