It was left to an adventure photographer, Ross Bernards, to disclose evidence on Instagram. Mr. Bernards, 34, of Edwards, Colo., was visiting the monolith on Friday night when, he said, four men arrived as if out of nowhere to dismantle the sculpture. Mr. Bernards had driven six hours for the chance to ogle the sculpture and to take dramatic photographs of it. Using upscale Lume Cube lights attached to a drone, he produced a series of glowy, moonlit pictures in which the monolith glistens against the red cliffs and the deep blue of the night sky.

Suddenly, around 8:40 p.m., he said, the men arrived, their voices echoing in the canyon. Working in twosomes, with an unmistakable sense of purpose, they gave the monolith hard shoves, and it started to tilt toward the ground. Then they pushed it in the opposite direction, trying to uproot it.

“This is why you don’t leave trash in the desert,” one of them said, suggesting that he viewed the monolith as an eyesore, a pollutant to the landscape, according to Mr. Bernards.