For a temporary solution (Don't try using duty finder again after doing this, you'll just end up in the same situation again.)

    First, quit the game entirely, for about 5 minutes or so. You should be auto-booted from party. (You'll still be bound by duty in another world.)
    Second, after you are out of the party. Join a duty finder, then IMMEDIATELY leave the duty finder. You should instantly get back your friendlist after doing this.


DO NOT move to another area after doing this fix. You will be stuck in limbo again.