Deleted messages? You didn't say that in your OP. Are they really deleted? Just because you unfriend someone/block them doesn't delete your posts. There is a "game" that I know some people play where they look at their older history posts. You can look at the people who liked something or commented, and then see if you are still friends or not. I know for a fact that some people have blocked me but still have posts on my wall. Just because you are blocked doesn't mean your comments are deleted.
If however you legit deleted them, then no one can see them. Even you.