Small Aircraft
Flight Crew Private
Flight Crew Last 90 Days 10; Flight Crew Total 1950; Flight Crew Type 1320
Human-Machine Interface; Communication Breakdown; Situational Awareness
Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Aircraft; Human Factors
I departed ZZZ1 for a short VFR flight via pilotage to ZZZ for a full stop landing. Departed ZZZ1 using CTAF 122.725. Enroute I switched to ZZZ CTAF 122.7 and monitored [the] frequency. Reported my position 5 miles out; entering downwind; downwind; base; final; and clear of the active. Did not see or hear conflicting traffic.Later flew from ZZZ to ZZZ2 for lunch and return. Upon engine start [discovered] radio still tuned to 122.725 for ZZZ1. Left aircraft at ZZZ for scheduled annual inspection. Got automobile ride back to ZZZ1 with a friend. Upon reaching ZZZ1 by car; another pilot alleged that I had flown 100 ft. above a trainer [aircraft] operated by [a flight school] in the pattern while landing at ZZZ. I did not see or hear radio calls from conflicting traffic.I believe that a contributing factor was that the radio was still tuned to 122.725 ZZZ1 CTAF instead of ZZZ frequency; which still displayed on the stand-by frequency. Either I had failed to press the button to 'flip' the frequency between active and standby; or in turbulent air pressed the button twice. Corrective action is to double check frequency change after entering frequency. Make sure [the] frequency change was actually accomplished.
Pilot reported being informed of a NMAC; by an eye witness; after the flight was complete.