At approximately 0800 mountain time, a Mooney M20B was damaged during a forced landing on rocks near Loa. The pilot and passenger were not injured. The pilot said the engine quit about 15 minutes after departure, shortly after he slid his seat back to retrieve something from the back seat. During the forced landing, rocks ripped open the wing and damaged the nose gear. Examination of the airplane revealed the fuel selector valve, which is located under the pilots seat, was between the right and off positions.