Because of some technical issues in the forum platform, facebook login is no longer available. If you used your facebook profile to navigate in the forums and you don't want to lose your identity (Or keep it secret under the same alias because, you, know, that's what thieves do ) there's a workaround for this and you can recover your account following these steps.
Click "Forgot password?" on the sign in at the top right of the website.
Write your email associated with your facebook account and fill the captcha to prove you are just a thief.
You will receive an email "Password recovery information from King of Thieves" and a link redirecting to the forums asking to validate you really did this action. (If this fails, there's another link below in the mail with your user ID and a validation key)
Once again in the forums just click to validate your action, this will send you another email, "Your new password King of Thieves".
There you would find your username (which should be your facebook name), the email you used to recover your profile, and a temporary password that you will use to log in and then you are supposed to change because if you can remember that, then you shouldn't be a thief after all.
You will keep your forum name, your facebook name (username) will remain hidden so you don't have to worry about that.
PS: I didn't really try to use my facebook name as my username (but I did try my email and it didn't work) and try the same password before I went through all these steps so that would be up to you to test.
Hope all this works for you too!