If you want to block someone on Facebook but Facebook can't locate that person - does that mean he or she has already blocked you?

Facebook server sometimes crashes and is slow and if you can't find that person there can be other reasons too.They could have deleted their profile,changed their name or marked their profile as unsearchable.And in the end it means they have blocked you.
But you can verify that by searching for that person on google.Of course there will be a few people under the same name but google will find the pages on facebook and then you can click on the link that you think is the person you are looking for.
Before you do all that sign out of facebook.When you find the person on google go their profile and bookmark or save the link.Then sign in and open the link.If it shows something like error or that wrong link or something like that then yes you are blocked..