I;ve sat on this comment for a couple of days.

I really do feel for the family.
Now I would like to ask a question.
If he had a cell phone and it was turned on it was transmitting.
Could the signal have been received by a govt approved portable scanner?
If the signal could be received by a scanner could the scanner be installed in a helicopter searching the area? As I asked above, if a unaccounted for signal was received would that have been enough information to allow searchers to home in?
At one time civilian scanners had the ability to scan cell freq's but that feature is now banned. I expect these scanners are still available to L.E. agency's.
And what wrong with the idea of flying with a portable cell system (if one exists) something that CAN originate and receive a cell call? In that type of terrain a signal will only reach a couple miles. Find the target signal, phone and then let them direct the search.
All that can be done now is send condolences to the family and hopefully learn from this mistake.