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With you reporting the car it would tend to indicate that you simply found the car and had no involvement in its theft. The police would have to have some additional evidence that you had something to do with it other than a fingerprint as you might have entered the car to see if there was any identifying information that would allow you to notify the owner.
There is nothing that would prevent them from looking at you as a "person of interest". If the police do decide to file charges for theft, do not make any statements to them and request that you have an attorney appointed to represent you. If there was no damage and the car was recovered intact, I would find it unlikely that they would pursure it without any further incriminating evidence.
Unless the police can get additional evidence pointing to you such as witnesses or physical evidence that you had something to do with it, I don't see them being able to make a case against you.
With that said, it would seem odd that a car would either be towed there and left or that one would sit there long enough for this to occur without someone noticing it....
But merely finding a stolen car and leaving a fingerprint from where you inspected it would not likely hold up in court for any type of prosecution.