Well, the only reason a fic would be removed from the list is if the writer is repeatedly offered review exchanges which they make no reply to, so they'd have plenty of notifications of that happening. (Users are supposed to tag someone they want to make a deal with.)
You do, however, raise a good point. I don't imagine anyone but me will be removing fics, so I'll be sure to tag a user when removing a fic. Thanks for bringing this to my attention.