Hey Wallflower.. Unfortunately we live and learn - and this industry comes with a LOT of learning curves. The number one rule is to always have contracts in place. The contract should essentially say that by you providing your free redesign service, that they agree to get you to do the maintenance on the site etc.
I am not sure if you have already handed over the open files and such to the client? If not, I think you should go to them with a contract and ask them to sign it. At the end of the day, by you giving those files to this character who knows little about design etc, he could easily try to pull it off as his own.. that's a concern.

One thing we know though is that you won't make this mistake again Good luck!