Its rough out there in the streets

That car is under a tarp somewhere until it can get a new grill. I sold a car to my deadbeat neighbor $200 a month for a year and then he would get the pink with a $100 penalty for every month he misses, wrote up a contract and he signed it. Stupid but I thought the guy wasn't going to move out in 2 months! So I lose contact with the guy and about 5 months later I get a call asking for the pink so he can register it. I told him your now $2600 in the rears and when I see $2600, you get the pink per our agreement and BTW that car is going to be reported stolen in 2 weeks if I dont hear from you. Nothing...so about a month later I'm driving home and I see my F'n car parked on a residential street in the next town! I run home and get the pink and knock on the door of the house. Find out He's not home and the mom doesnt know where he is. I call the tow truck that I asked to park around the corner (a customer of mine) and he comes and looks at my pink and starts hooking it up. About 2 minutes later the guy runs from around the corner and starts threatening me and the tow truck driver if we take his car! I start calling the police on my cell, the tow truck driver tells me he doesn't want to get in the middle of anything and leaves. The guy tells me if I call the cops, the car will disappear and Ill never see it again, or the money. Im screwed so I tell him Ill buy the car back for what he has paid me, $400. He says it was $600 so we settle for $500. Long story but if someone wants to hide a car, it can be done.
What does that equate to "posession is 9/10 of the law" ? as in the guy possesses it so it is his? It seems if you had the pink its legally yours.