Pantaleoni was last seen riding his rusty 10-speed bicycle in Maunawili Trails on the Hawaiian island of Oahu at approximately 9:00 a.m. on June 28, 1995. His bicycle was discovered abandoned near Kailua. It had been chained to a fence surrounding a water tank by a hiking trail. There was no sign of Pantaleoni at the scene. He has never been heard from again. Foul play is a possibility in his disappearance.