How can i get my car back?

My uncle brought me a car for me last year which I took to the DMV and had changed over to my name. Unfortunately I crashed and my uncle took it to a mechanic that he knows and they probably released it to him without my authorization because once again its his mechanic. My uncle is now incarcerated and I don't know where he is and I haven't talked to him since he's been in there. My step aunt knows where the car is but she is withholding the car from me because she is very envious. She actually asked me for my drivers liscense number and birthdate and ss number but I decline because I don't trust that. The car may be destroyed if I go to the cops and report it stolen. What can i do the car is the only thing i have and it is still in my name because I had the police run the plates yesterday. I have the vin number and the plate number