Kneifl was last seen in his hometown of Sioux City, Iowa on February 14, 1983. He left his girlfriend's residence at 9:30 p.m., driving his dark brown 1981 Cadillac Fleetwood with Iowa license plates numbered HIZ379. He has never been heard from again. Kneifl's girlfriend of several years and her daughter reported him missing after he failed to show up the next morning to drive his girlfriend to work.

Kneifl owned and operated a dry cleaning business, Fethke Cleaners, in the 1200 block of west 26th Street at the time of his disappearance. His wife helped him run it for over thirty years until her death in 1978. He previously served as the mayor of Hartington, Nebraska. He was the only mayor in the city's history to be elected with write-in votes. Authorities believe he was taken against his will. His case remains unsolved.