Q: I checked my @me account and everything was gone.  What happened?

Where did you check for your data?  On the various apps like Contacts and the email cliend?  Or did you log into icloud.com with your computer (this is the way to check whether the data is really gone).

I'm afraid you have to remember the password you first used for your icloud account.  On the mac, go to system preferences>icloud.  Click the Account Details button to see the ID.