The non-certificated pilot of the unregistered two-place weight-shift trike was flying over his ranch when its 65 horsepower engine suddenly lost all power. Although he was able to descend to a successful power-off touchdown, during the landing roll the trike encountered rough/soft terrain, resulting in the overload failure of the nose gear strut. The nose of the trike then dug into the dirt, and its airframe nosed over onto its back. The accident was eventually reported by a family member of the passenger, and the Federal Aviation Administration Inspector who went to the ranch to interview the pilot reported that the pilot had already disposed of the airframe and the engine because of their extensive damage. The pilot said that he had no idea why the engine lost power, and that he completed a preflight inspection prior to the flight. No further determination could be made as to the basis for the engine's loss of power.