Question on estate law?

My father died and the only real possession he had was a car that was formerly my great-grandmothers. My grandfather told me that since the car was in my father's name, I'd inherit it since I'm the only child. That was a year ago and I haven't heard from him again. And my aunt has been driving the car as if it was hers, even though she has a brand new car. Nice family, right? In the meantime, I lost my job and could really use the money from selling the car. So, my question is this: what, if anything, can/should I do and is there some way he avoided probate or something? Any advice/information is greatly appreciated.