Hammerle was last seen in Manhattan, Kansas, on August 22, 1981. He departed from a birthday party in the 1000 block of Poyntz Avenue, accompanied by Joseph Grasher. The two left in a red van with a group of people. Neither Hammerle nor Grasher has been heard from since. At the time of his disappearance, Hammerle was paralyzed from the waist down and relied on a wheelchair and a colostomy bag. He also suffered from cluster headaches and had undergone the extraction of all his upper teeth.