Dingler was last seen at approximately 5:00 p.m. on August 10, 2005 at his residence in the vicinity of the 5000 block of Coventry Court in Boulder, Colorado. He left his home driving his white four-door 1996 Honda Acura with Colorado license plates numbered 776 JEM. He has never been heard from again.

Authorities believe Dingler may have been trying to return to his former residence in Coal Creek Canyon area of Gilpin County, Colorado; he had moved from there shortly before he disappeared. There were possible sightings of Dingler wandering around on several golf courses, including the Ute Creek Golf Course in Longmont, Colorado, after his disappearance. By the time police went to investigate the sightings, however, the person resembling Dingler was gone. Dingler was carrying $100 at the time of his disappearance. His loved ones stated he would be unlikely to go to any major city, as he does not like large crowds of people.

Dingler's vehicle was located abandoned on August 31. It was found stuck at the end of an unpaved ranch road in Hanna, Wyoming. Dingler's wallet, money, and identification were inside the car, as were the tan trousers he was last seen wearing. A map of Colorado was also found. There was no sign of Dingler at the scene and no evidence as to where he had gone. Tracker dogs traced his scent seven miles to a highway, where the trail was lost. Two witnesses stated they saw Dingler walking down that highway on August 16. He was wearing only boxer shorts, and they asked him if he needed help or a ride somewhere, but he declined assistance.

Dingler has never been located and his case remains unsolved.