Tennison was last seen in Humboldt County, California on January 19, 2009. He had gone there with his son and a friend, and planned to finish a construction job and get paid for another job before returning to his home in Keyes, California. Later that day, Tennison's son and his friend went back to Keyes. They expected Tennison to finish his job and then take a bus home a few days later. He never returned and has never been heard from again.

Since Tennison's disappearance, there have been persistent rumors that he was killed. His family stated he was close to them and wouldn't have abandoned them, particularly his four sons. He has no history of mental illness and although he used marijuana recreationally, his loved ones say he wasn't involved with hard drugs. Stanislaw County, California law enforcement are investigating his case, which remains unsolved.