But to do so, if you become a moderator/admin (I don't know if moderator is valid) there is a little box thing at the top of the wall, when hovering your mouse over it you can show/hide deleted posts.
Ok never mind, you need to an admin, and then under the "Wright somebody a message" thing there is a thing that says "View" hover your mouse over it then it will say "Hide deleted" uncheck that and it will show the deleted messages.