.. and that same "manager" also is identified through phone records as being an employee of the local Pac Sun store.
Might we expect he and MC had crossed paths at one time or another at Pac Sun, and now possibly at the car wash? If so, we might expect the "manager" to at least be somewhat visually familiar with MC but then again, how many of us could remember one teen of the very many that probably visit that Pac Sun store?
MC attempting (at least the attempts were from her phone; by whom, who really knows at this point) to dial the same ph# six times simply wreaks of 'urgency'.
If it indeed was the "manager" MC was attempting to contact (THIS IS MY SPECULATION), was it that she was being forced to drive to a/the car wash and MC was hoping he was there to help her in some way, i.e.: she was afraid to call police with a perp sitting next to her?
Something else comes to mind: since LE knew MC's car was driven through the car wash because of the receipt(s) found in her vehicle, they might have floated the 'story' that the attendant claimed to have witnessed MC there with a 'male' passenger. That might have been an LE attempt to freak the perp, wondering if he indeed had been identified in some way.
At this point, we might fathom that LE does not know what occurred at the car wash. Also, the receipt(s) might be dated for earlier than 02/09/2010.