The things that have kept coming up in my mind are:
1. IF there was mud on the tires: Was there mud on the sidewall or just in the tread? Is it just a trace of mud or a significant amount? If there is mud on the sidewall, the car was at the location after any significant rain event, as the rain would have rinsed the mud off of the sidewall. If there was mud in the tread, the car was moved to the area while the ground was still damp enough for mud to stick to the tires, presumably from the area the car was found, as the mud would have dislodged from the tire when driven on paved roads and only left a trace amount.
2. Were there any tracks in the dirt area where the car was found? Tracks could be from the car tires, footprints from a person exiting the car. IF there were tracks, then there was not a significant rain event after the car was left there. IF there were foot prints, where did they lead? Was there another set of tracks of a vehicle (car, bicycle, etc) that would suggest multiple people participating in leaving the car?
3. When the car was found, stripped or not, was there dust on the car? IF there was dust on the car, the car 1. had been there for a period of time to collect the dust and during a period of time when the ground had dried 2. had not been there during a rain event.
4. IF the car was locked with the key fob inside, IMO, someone had a second key fob. Who could have a second key fob for a loaner vehicle? 1. People that have access to the key fobs at the dealership where the car was from. Which could suggest that 1. a key fob was stolen from the dealership or 2. someone from the dealership was involved. Did the dealership have any theft or break-ins? Can you get key fobs on the black or gray markets? How does the locking system work? Can you "override" the locking system?
A google search for this question result gave this direction via YouTube
What were the settings on the Porsche in the AW case?
5. What was the starting and ending mileage and the gas level on the AW loaner car? Who else had used the loaner car?
All MOO and speculation.