Thompson was last seen at his residence, which is located in the vicinity of the 5000 block of Hess Road, off Highway 138. He left intending to go on a three-day camping trip in the Salton Sea area, traveling on the Colorado Aqueduct to the Colorado River where he had a houseboat in the Park Moabi area, approximately 10 miles southeast of Needles, California. Thompson apparently never arrived there, however.

On September 23, six weeks after his disappearance, Thompson's car, a light golden-brown 1986 Buick Skylark, was found disabled in the middle of the desert, four miles off Highway 177 on Phelan Pass Road, seventeen miles north of Desert Center. There was no sign of Thompson in the vicinity. Authorities speculate he may have camped there for the night. A campsite was found about three miles east of the vehicle. At the site authorities located a full can of beer, Thompson's knife, and an unopened pack of cigarettes.

Thompson is described as an enthusiastic outdoorsman who has enjoyed camping in the desert wilderness since his childhood. His family says, however, that it is uncharacteristic of him not to contact them. He had worked as a foreman at a telecommunications company in Los Angeles, but quit a few days before leaving his home which was behind his mother's residence.

Since Thompson's disappearance there have not been any unusual calls detected on his phone bills, nor has there been any sign of him at his houseboat or any activity on his driver's record or Social Security number. He was not depressed at the time of his disappearance. His case remains unsolved. Some agencies state that he disappeared from San Bernardino, California.