Coachella and the surrounding area have infinite places to dispose of a body so that it would never be found. Add to that that there are THOUSANDS of abandoned mines out in the desert and these two factors are the main reasons I am highly skeptical these two made it to Beaumont that night, despite what the tracking dog indicated. If someone had ill intentions toward Audrey and/or Jonathan, it would make more sense to handle things out in the desert versus going toward LA (their direction relative to where Audrey was last seen). Where her car was located is certainly not in the middle of nowhere and the further west you head on I-10, the heavier populated it is.
That makes a lot of sense. We don't know what Jonathan's phone was doing, other than powering down. But Audrey's phone did not ping outside the East Coachella Valley on the 10th. And that places her either in Coachella or south of Coachella, traveling in the direction of Brawley. She doesn't appear to have been going in the direction of either Beaumont or Palm Desert.
Audrey told her sister she was picking up Jonathan who was coming from Brawley, so it makes sense that whatever happened to them, was, at the very least, initiated near to where her phone last pings.
The way her SUV was parked, it would appear that the passenger side would have been difficult to exit. It really looks more like a dump, than a deliberate stop.
I have to wonder if they aren't still, very close to Coachella.