On or about July 12, 1993, at 1400 Pacific daylight time, a Cessna A188B, N5858G, collided with the terrain during the landing roll near Rockford, Washington. Visual meteorological conditions prevailed at the time and no flight plan was filed for the local aerial application flight. The airplane was substantially damaged and the private pilot was not injured. The accident was not reported until March 18, 1994, when a Federal Aviation Administration Inspector in Spokane, Washington, received a call from a witness who reported that the accident occurred sometime between June 1993 and August 1993. During a telephone interview, the witness reported that the pilot entered his workshop and the pilot stated that he damaged the airplane. The witness accompanied the pilot to the airstrip and helped the pilot move the airplane into a hangar. The pilot stated to the witness that during landing, the wing caught in tall grass and that the tailwheel separated when it collided with a gopher hole. The witness stated that one wing was damaged, the tail section was "torn up" and the fuselage behind the cockpit was "tweaked." A Federal Aviation Administration Inspector at Spokane, stated that he saw the airplane when it was being repaired, but did not realize that it had not been reported. During a telephone interview, the mechanic who performed repairs on the airplane stated that he performed a major repair and alteration to the empennage of the airplane, but did not know how the airplane was damaged. To this date, the National Transportation Safety Board has not been notified, by the pilot, that the accident occurred. The pilot's attorney reports that the pilot denies that there was an accident or other occurrence which would require reporting under Part 830. The date and time of the accident were arbitrarily selected for the purpose of this report.