Q: Apple ID stolen and modified

I cannot log in to App store from this Monday on. Shortly after that I realized someone hacked my password, so went to change it back. Very weird that I was asked for Recovery KEY. WHAT THE **** IS THAT? Cause I had never seen that a thing before. I called Apple Support, who told me that NO WAY to change password without that KEY.

I almost took it as my own fault forgetting Recovery Key, until I checked thought my email box. I used email name as my apple ID, so every action on my apple ID was sent to me by email. By tracking those records, it is very clear that the hacker changed my password, and then, set up the **** Recovery Key for me! What can I do if both the password and Recovery Key are in someone else's hands???  One more thing upsetting me is, how did the hacker manage to pass my security questions check to change password and setup recovery key???

Anybody also encountered this kind of problem? It took me several hours to talk with apple staff but it disappointed me deeply that they could do nothing but send me some links which actually I can find by myself.