Selling Question

Howdy folks I need some help pleasein Texas. I move out of my house in June and was making steady payments but let the insurance lapse. It is owner financed and he called me last month and said that rather than foreclosing on the house we could just sign it back over to him, at which point I stopped paying on it so technically I am 2 months behind. Well it has been almost 2 months and no paperwork yet. Today a friend of mine drove by there and saw someone else has moved into the house. I want to try and find out who they are, contact them and sell them the house myself. I don't know if they have signed any contracts with the guy I bought it from, but wouldn't they be void seeing that I still tachnically own the house. What can I do to keep from losing all the money I have invested in it. I appreciate any help or suggestions I get