Looking at a map, I think they took Hwy 76 to Hwy 79 (79 takes you over the mountain and into La Quinta). They may have turned onto 79 and continued and missed the turn to stay on 79 and instead went straight, which would lead them to where they were found.
I've driven in the area and I think I would have gone that way instead of all the way west and around.
There is no way to go straight at the turn. The road ends and you can only turn left or right.
Once you get on 79 it does not fork. It looks like they would have had to turn on to Chihuahua Valley road. It's a deliberate right turn and leads to dirt back roads by the scout camp.
But there is no way to know why they did. There was nothing back there if they needed help. And had they gone just a couple miles up they would have found a gas station on 79.