On or about September 3, 2000, at an unknown time, a Cessna 172P, N531PC, registered to and operated by Auburn Flight Service, was substantially damaged at an unknown location, and by an unknown pilot. The Chief Flight Instructor from the operator reported that the aircraft is used for rental purposes and has flown 99 hours since the last maintenance inspection dated July 25, 2000. On about September 4 or 5, 2000, a pilot reported that during the pre-flight inspection, he noted wrinkles in the skin on a wing. A mechanic looked at the aircraft and reported that it was okay for flight. On September 7, 2000, the aircraft went in for the scheduled 100-hour inspection. During the maintenance inspection, maintenance personnel reported that three ribs in the left wing were buckled, the spar was damaged, and the upper and lower skin sections were buckled and oil canned. The cabin top assembly skin was buckled and wrinkled. The horizontal stabilizer forward spar and reinforcement were severely buckled and cracked in the center section.