Your CD key is the only thing that's worth value. Your GS account isn't linked to it, all it contains is your email, friends list and a few other server stored tid bits.
How did someone try stealing your account? I think that needs some clarification.
Because someone logged in with the same name at same time, it said it found user with the name and it logged me off. When I logged in back everything was ok though. But they could do certain modifications to servers to steal things, I mean they saw I am the only registered user and tried to use my account.