Quote by IRiSH OH:
Your multi-player stats and unlocks were still there because the multi-player stuff is saved on Infinity Ward's servers. He's having problems with the single player campaign. As far as I know, no game has ever saved single player progress on an online server.
My best advice is to try what Ralph said, unplug from the internet and then delete the whole COD4 "folder" and clear you system cache. From what I'm reading though, there are a lot of other people that have this same problem and have yet to find a solution.
In parting, STOP CHEATING! Let this be a lesson to you for the future.