Kind of stayed out of this, as there is always 2 sides to a story, but just to throw my two-penneth in, then I will leave this little nugget
1 Basic definition of theft
(1) A person is guilty of theft if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it; and thief and steal shall be construed accordingly.
Basically from what you have been saying then I can't see how it can be theft as there is no dishonesty involved in your appropriation of the property (car), unless I am very much mistaken, seems like a civil matter all the way to me, but then again what do I know
I think you need legal advise my friend.