Idon't think it is "stolen" in the eyes of the law.
I felt I had no choice but to give it to him, so he would keep his mouth shut.
That is an exchange for service: plane for silence. You gave it to him. If you take it to small claims court it will be a he said/you said on whether the nmodel was an exchange for earlier services in the ARF build. It will just get ugly.
Next time, either write it down as a signed and dated contract or just accept that some folks are garbage and do these things.