"Going somewhere" can include lots of varying options (going to get coffee, going to get drugs, going to some place or to see someone, or who knows what) and I agree (and have been saying for quite some time now) that the planned go-and-return scenario fits so well.
Following that, I can see them getting back to the Shops area to return her to her car (as planned all along), and then things go awry as they get close. To me, the fact they there was a return, that wasn't detoured until the last minute, hints that things were still going okay until then.
Maybe it's at this point, after a ride, that EA decides it's time to make his "move," and it's his last chance of the night - - and then he gets rebuffed. Shot down for a 2nd time in the same evening, things get ugly from there as he explodes? I can see that.
We do know that at some point, she ended up IN HIS TRUNK according to LE, so there's no way they went somewhere and back without - at some point - him going wacko on her. It's just a question of where/when imo. (Not saying I know the why, but LE thinks they have figured it out, and I'll go with that.)
And whenever he went wacko on her, her phone use would have stopped--no more texts, phone calls, IMs, etc. If LE has complete phone records, and I would assume they do, I would imagine there is a pretty clear picture for their timeline.
I do think the scenario above is quite possible, and I hope the areas of the Shops close to the last pings have been checked for places with damage that might have been caused by a car. Or would that be impossible to find? I don't know the area at all. Sooo many possibilities of how the car damage occurred--honestly, I've wondered if they fought in the car, she managed to get out, and he ran her down. Maybe she was in the trunk, came to, pulled the latch, startling EA into running into a guardrail or something. Maybe wherever he took her out of the trunk, he hit something because he was agitated and in a hurry.
Iirc, according to a coworker, EA had shown interest in CM because he had shown her picture at work prior to this incident. By the time he and CM return to the Shops and her car, he tries to make a move, and it goes horribly awry, and she goes missing.
One additional thing, for me, is that LE believes she was in the trunk when EA went home, which leaves at least some possibility he had help after the fact. But the timeline we do know, and SteveS's scenario with timeline above, makes me think this is all EA, unless instead of the driving to leave CM somewhere, he had help, and he was home cleaning the heck out of his car before going to work.
Best for me to remember, LE has lots more info, and I bet they have a pretty good timeline in hand. Back to reading and trying to catch up!