Back to the local cop angle, or security guards from the hotel. Or someone driving around in a car that looks like a security guard. Gives people a warm and fuzzy, shakes a few hands, ensures them that their cars are being looked after. The guard selects a few plum cars that are in good locations for a heist. Bing, bam, boom.. the car is gone in 45 seconds. The guard is never to be seen after. The hotel knows nothing about an outside security force on the premises.