Stop worrying about skyrim, worry about your bank statement at the end of month, cancel your credit card.
If he had CC info stored with Steam, and assuming he was hacked, the only thing he has to worry about is the hackers buying stuff on his account and then probably gifting it to people. They cannot pull his CC info out of Steam--all they'd get is the last four digits and expiry date, IIRC.
@ the OP - chances are it's a client error. However if it's not and you have indeed been hacked, you need to do the following ASAP: 1) contact Steam Support. Create a Support account (unique & separate from your Steam client account) and submit a ticket. It might take them a few days to get to it; Steam Support times really vary sometimes. You will need to provide some proof that you own the account, as outlined https://support.steampowered.com/kb_article.php?ref=2347-qdfn-4366. Do this with your initial ticket to save time.
2) Change your email password. Make it unique and secure. This is just a precaution if you didn't enable Steam Guard; without Steam Guard, the alleged hacker can access your Steam account (if they know the password) without also needing access to your email account. With Steam Guard, they also need your email.
3) Change your Steam password once you get the account back. Again, make it unique and secure. Your email password should not be "skyrimizawesome1" and your Steam password should not be "skyrimizawesome2."
4) Once you get control of your account back, go to Steam -> Settings -> Manage Steam Guard Account Security. There's an option there to enable or disable Steam Guard. If it is not enabled,
enable it immediately.
...Actually, even if it's just an account error, do that last step anyway if you haven't already. Although I think Steam Guard is usually enabled by default. Yes, it can be sort of annoying. However, that little annoyance, when combined with a secure email password,
will save your account in the event someone tries to access it. Even if they have your username and password.