OMG. You can't get it back. Atleast you must have remember any informations about that account.
Here are the steps:
1) Recall the Informations about your friend's CrossFire Account.
2) Submit a ticket to the forum.
3) Contact the z8 staffs.
I only know how to retrieve accounts in CF Philippines.
BTW, what is the reason why your friends account got hacked ?
Are you referring to a 1 friend or more than friends because you said the word ''FRIENDS''
~Thank me if I help :P