I'm no legal expert at all so please take my advice w a grain of salt but...
I bought my neighbors car out his driveway as a project car. Never registered it in my name. Never signed the title or anything. Just paid him $200 cash and he handed shit over
When I needed to get rid of the car, I called the local scrapper who picked it up, took the title, and gave me $200 cash
So all that to say, if the seller didn't steal the car I think you're good