Your gut doesn't lie.
I had the same kind of situation a while back. Guy never pays, never responds and then claims I never sent invoice, never replied to messages, etc.
He gets a strike and some months later e-mails me essentially asking me to name my price to clear the matter up (remove the strike). I guess eBay told him he was on thin ice. He never did get NARU'd as far as I could tell but somebody else must've given in to him as it wasn't me..