We’ll never know of course. But I suspect this is the same thing that happened on mh370.
Sure seems that way.
The interesting point about MH370 is that the co-pilot's phone, which had been turned off prior to takeoff, made contact with a cell tower that the airplane passed after breaking off contact with ATC. That suggests the co-pilot turned his phone back on after being locked out. I suppose being locked out would be a good reason to turn on your phone, even if no service was available at the point in the flight.