That's easy- the guy that arranged for it to be stolen. If it wasn't an insurance job, it still had to be someone with knowledge of both the car and the shipping arrangements. If the car was stolen by "accident", it would have already appeared somewhere. It's happened before with trailers that were stolen with well-known cars inside, the car magically appears somewhere after the publicity starts to get around. The theft happened for the trailer, the car was bonus, but when the car attracted attention it gets left somewhere. Not always, but it's definitely happened.
But I seriously doubt that some person who stole that car at random because the opportunity just came up, without knowing what it was, would hold onto it once all the publicity hit.
