Bordenkircher was last seen on June 12, 1965. His family was on a weekend visit to their cabin on Beaver Street in North Lake Tahoe, California at the time, and his parents were unpacking. Bordenkircher was last seen playing on a wooden swing in the front yard. He has never been heard from again.

An extensive search of the area turned up no sign of Bordenkircher. Nighttime temperatures dipped near the freezing level in the days following his disappearance and he was not dressed warmly enough to have survived long in the outdoors. Investigators initially believed he drowned in Lake Tahoe, but his body was never located, and he would have had to walk half a mile over rough terrain and cross a major highway to get to the lake. His family believes he was abducted by someone who wanted to raise a child. His case remains unsolved.