“… Grand Teton area and most of WY is very desolate.
Good luck unless a cell tower helps but most of WY has limited or no service .”
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I don’t know what kind of vehicle they had on the trip but many modern cars’ computers and even key fobs can store GPS (and other) data that can be retrieved for location related information. Not retrievable by the ordinary owner but retrievable by the car company and the authorities under warranty. That is likely one of the reasons they impounded his vehicle and also one of the reasons why the DIRTBAG’S attorneys will advise him not to say anything to the authorities.
They can track their Cell Phone locations throughout the Trip.
I’m sure they are doing that as we speak.