On July 6, 2001, approximately 1000 mountain daylight time, a Griffith-Boyd Lancair 360, N15EG, registered to and operated by the pilot, was substantially damaged during a wheels-up landing at La Junta Municipal Airport, La Junta, Colorado. The private pilot-in-command and the commercial flight instructor-passenger were not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the personal flight being conducted under Title 14 CFR Part 91. The flight originated approximately 0800. The following is based on the pilot's accident report, written statement, and several telephone conversations. The pilot was flying the airplane. In preparation for landing, he slowed the airplane and extended the landing gear. He heard the usual loud aerodynamic noise and observed three green lights indicating the landing gear was down and locked. However, during the landing, instead of touching down on the wheels, the pilot heard a loud scraping noise and the airplane veered slightly to the right. It traveled 300 feet on the runway and another 300 feet on gravel next to the runway before coming to a halt in a ditch. There was damage to the fuselage skin and bulkeads. The pilot inspected the airplane and found all three wheels were in their respective wheel wells. The main landing gear doors were partially open, and there was hydraulic pressure on the right inboard door. He rechecked and found the landing gear control in the DOWN position. He suspected that when the airplane touched down, the landing gear retracted and he submitted evidence to support his conclusions. He found the UP RELAY to be hot to the touch even though the gear switch was in the down position. He noted what appeared to be the beginning of a mouse nest in the center console where the gear, flap, starter, and power wires pass.