On July 17, 2016, about 0930 mountain daylight time, a red and white colored Cessna 172 airplane, N8184B, was substantially damaged during a mid-air collision near Emmett, Idaho. The private pilot was not injured. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight that departed Emmett Municipal Airport (S78), Emmett, Idaho, at approximately 0920. According to the pilot, he departed runway 28, and flew the left hand traffic pattern during his ascent to 3,500 feet mean sea level. After he exited the traffic pattern on the downwind leg, the pilot flew east for approximately 2 miles and then turned northeast. About 10 minutes into the uneventful flight, he received a radio call from another airplane on the airport's Common Traffic Advisory Frequency (CTAF) that stated "aircraft east of Emmett…we almost got you." The pilot had not observed any aircraft in his range of view and elected to continue the flight. He landed about 40 minutes later and parked the airplane, but as he tied it down on the airport ramp, he observed a tear in the airplane's rudder, which was accompanied by a stretch of blue paint. The pilot reported that he monitored the airport CTAF, and had not heard any reports from anyone near the town of Emmett or transitioning through the town during the flight. He further stated that he did not observe any damage to the rudder before he departed. The pilot did not feel any sudden movement of the airplane between his departure and the time he received the radio call. Postaccident examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed substantial damage to the airplane rudder, which displayed a lateral tear and a blue mark at the trailing edge of the control surface. The other aircraft was not identified at any point during the investigation. A review of FAA radar data from 0820 and 0840 showed a total of three radar targets that passed through the town of Emmett. Two of the targets appeared as VFR primary radar targets, and did not display aircraft registration numbers. According to the pilot of the third target, identified as N471AM, he was on a cross country flight from Cascade, Idaho, to Nampa, Idaho, and was following a friend who was flying a brown and orange airplane. The pilot stated that he did not encounter a near mid-air collision at any point during the flight, and photographs of N471AM revealed that the airplane paint scheme did not contain any traces of blue consistent with the mark on the rudder of N8184B. The FAA Airplane Flying Handbook states, "Collision Avoidance All pilots must be alert to the potential for midair collision and near midair collisions… This concept requires that vigilance shall be maintained at all times, by each person operating an aircraft regardless of whether the operation is conducted under instrument flight rules (IFR) or visual flight rules (VFR)…Most midair collision accidents and reported near midair collision incidents occur in good VFR weather conditions and during the hours of daylight. Most of these accident/incidents occur within 5 miles of an airport and/or near navigation aids."