Unfriend Finder is a plugin that lets you see who has unfriended you on Facebook. For more information check out:
Once installed, you'll see a new left- hand filter on Facebook. The Unfriends filter will always be displayed on the left-hand side menu, where other filters are located.
Unfriends include those who have removed you from their friends list as well as those who have had their profile deleted or hidden. In the latter case, you can be notified if someone reactives their Facebook profile.
There's also an Awaiting Requests section that shows you the status of your friend requests: Canceled, Accepted, or Pending.