All great points. I was simply speculating.
With regard to possibly having a hint of suspects, I am not saying they knew for sure and that is if and only if, when they found her body that canvassing the area and talking to local LE there may have given them an idea of people who lived in that area and what they drove for a vehicle.
They also could cross check anyone living in the area out there or known to and they were doing a very active investigation with a team already assembled and at work. So to cross check people through vehicle record checks. I am not saying they were sure of anyone, just that they might find then that he matched up with a person from that area, which it did. Heck, if he had not run, had her phone or had blood in the car, etc. he may have just been able to drive away. He was stupid and in the same area where she was abducted.
I know nothing about the Rosewood area so it was simply speculation. However, I would not expect him to drive as new of a vehicle as he drives either... It is just that we do not know where he lives when in Columbia and in fact may have been living in Columbia or where friends/gf may live.
I wondered about robbery too yet on the other hand, what would a 21 year old college student likely have for money, etc.? Any credit cards etc. would leave a trail if he used them (not that he may be that bright). And he did have her phone...
The fact this woman was with him in that area in the wee hours stands out to me... I do not think she was abducted by him but that is simply because the terminology of saying she is "isn't what you usually say about most victims of abduction...
All just my speculation and opinion which may change with more info.