I have wondered if a mode s transponder could include he frequency that the radio is tuned to in its data return. That way if atc were unable to raise an aircraft on a frequency they would know what frequency it was on and either contact it or relay a message to change. It wouldn't help here but would prevent some hassle in other situations.
That is an excellent idea No_one and could be used world wide to enhance safety. Maybe send an email off to Garmin or some of the other big radio / transponder manufacturers (seriously). There's a few technical considerations to think about like multiple radios etc, but it certainly is a good idea to think tank.
It would shock many to know that many of us have flown into and out of CTAF airports without a radio for years!