There is no way the F-35 was flying without radar reflectors and likely even ADSB on. That said however if there was a major systems failure you loose tracking

There is no way the F-35 was flying without radar reflectors and likely even ADSB on. That said however if there was a major systems failure you loose tracking and even if you have a pretty good idea where the aircraft was it’s still not that easy to find in a wooden area.