The aircraft crashed in a steep nose down attitude in hilly terrain. Debris was scattered for about 100 ft but the aircraft did not travel after initial impact. The fuel tanks were ruptured and no fuel remained. The sheriff's deputies said no odor of fuel was noted when they arrived at the scene. The aircraft wreckage was missing for about 2 days. The pilot's wife last saw him on 7/30 at 2300 hours PDT. He reportedly left home that night or early the next morning. When he did not return on 7/31 the wife reported him missing. His car was found at Hayward Air Terminal, CA. There are no known witnesses to the accident. The aircraft wreckage was found by a rancher who was checking cattle on his property. No discrepancies in the airframe or engine were uncovered in the investigation. The wife said her husband had been depressed due to business. She said he had threatened suicide in the past but she did not believe he would take any action in that regard. An autopsy and toxicological tests revealed nothing out of the ordinary.