Go to some account Trade/Sell/Buy site.
Find post where someone gives MSN/AIM etc.
Add them on MSN/AIM.
Play some trustgame for a while.
Ask for the account name.
Go to
US WoW.com Account/Password Retrieval
EU https://www.wow-europe.com/login-support/
Enter something random to Answer and his/her MSN email to the email field.
If the email matches.. just send the email and wait