Sisco was last seen panning for gold with two friends in Happy Valley, Arizona on June 12, 1994. That evening he got into an argument with his friends; he wanted to leave and his friends did not. Sisco left on foot and alone. He has never been heard from again.

Sisco had two warrants out for his arrest when he disappeared; one of his friends believes he left of his own accord to avoid having to go to prison. Investigators, however, believe Sisco may have met with foul play or died of exposure in the desert. He left a young daugher behind when he vanished. His case remains unsolved.