>To make matters worse I was in a mountain valley and had no phone signal
I read the above as an indication that they were in a valley where mountains were blocking any chance of a signal. Going further "downhill" wouldn't help in that case.
Fair enough, I was thinking back to the time something similar happened to me "mid-mountain".
This Tesla must've been in one heck of a stop where "hiking wasn’t an option as it was pretty hot and we had no water", lol. Does Tesla make a motocross bike?
Lack of cell signal is still a problem in some parts of the U.S. I can think of a few places within a couple hundred miles where I can drive 45 minutes or so without any signal. It's also an area where triple digit temperatures are common in the summer.
I read the above as an indication that they were in a valley where mountains were blocking any chance of a signal. Going further "downhill" wouldn't help in that case.