In 2014, Kenny Veach completely vanished in the Nevada desert while exploring a cave characterized by a distinctive 'M-shaped' entrance. This is a clip was taken from one of his last ever videos.
On a YouTube video he wrote, "The entrance to the cave was shaped like a perfect capital M. I always enter every cave I find, but as I began to enter this particular cave, my whole body began to vibrate.
Detailed article on his disappearance: https://historicflix.com/the-mysterious-disappearance-of-kenny-veach/