Didnt think of the parental controls thing, +rep.
A renter Bnet'ed my account after adding a month of game time. All you have to do is call into blizzard and tell them you got an email saying your account was merged with a battle net account, say you didn't do this and suspect that a hacker did. Then they ask for your email + secret answer and un-merge your account, as well as send you a new password to your email. If anything happened to characters then just contact a GM and they can look into restoring characters / items.