Jamin, I hate to say this but, you will probably just end up making a new character. I know it's malarkey what happened, but it was probably your fault by joining a server with your username/password or simply because of windows security, and by that I mean all they would need to have is your IP address, and simply put that in as if it were on network neighborhood, and if you are sharing your computer, they can simply read the players.cs in your config folder and have your char's passes. (wow that was one long drawn out sentence, but it has lots of detail)
When I say this I don't mean to step over my boundry but, if I were an admin, I would re-create a character for you with the same levels/remort/items as your old one and/or clear Jamin and then recreate.
You might be able to get away with encrypting players.cs and have an extra tad of security (Win2k and XP only).