This person wanted to commission me for what he called a "butt icon". Basicly, it's just an icon that shows off underwear. I had lots of room for icons so he sent information to my email. I keep a work list, so I have him written down as paid. But mistakes happen, so I'm not entirely sure he has. I sketched it and sent to him but didn't get a reply for a while. So I gave him a poke on email, but noticed he was much more active on FA. I noted him there.
This is everything we wrote to each other, since I thought it might be easier then trying to explain everything: http://i54.tinypic.com/99ow2u.png
I'm not sure what to do. I can't refund him, which I would prefer at the moment, as I don't think he'll approve my updates. I can't work on the art, and I don't even know if he really did pay or not.
EDIT: Alright, so after listening to everyone's advice, I sent them a last note explaining I can still see history even if it's closed and if they can't give me the address, I'll have to consider it closed and not paid. They replied saying they haven't paid, so, that's that. Thank you for the help!