Who has legal rights to a car? The person whose name is on the title or registration?

My wife and I just recently started a divorce. I am out of contact with her. The title is in my name only. My name is also on registration but I cant remember if her name is on registration and since she is out of contact I have no way of looking. If her name was on registration could I legally get the car back since her is not on the title? I want the car back and am going to report it stolen but I want to find out about this. Thanx.