Well that sucks! Have you done a functional check on the radio to see what the problem was? Is it possible the battery either became disconnected in flight or gave it up ? A bad switch? Did you do a range check before the flight? Total signal loss on a AM modulation radio is unusual. Even if it's out of tune, it's going to show something. Here is some inspiration.
https://www.youtube.com/watch?v=HoLs0V8T5AA