Facebook lets you know every time you make a new friend on the social network, but it doesn’t tell you when you lose one.
You can check whether a specific person you suspect of unfriending you has actually unfriended you easily by checking their profile. If you are no longer friends, then that person has unfriended you.
When the Facebook timeline feature was launched, users quickly exploited a loop hole and were able to find out who unfriended them by comparing their friends lists in different sections of the time line. Facebook has since fixed that.
Who Deleted Me is an app that uses the same concept of comparison to determine who has unfriended you. It can be used as a browser extension for Google Chrome, Firefox, Opera, or the app can be downloaded to iOS and Android devices.
Start using it by signing in with your Facebook credentials. It will get your current friends list. Then when you need to check if anyone has unfriended you, it will get your friends list again and compare. With this comparison it is able to identify missing friends.
Missing friends are either people you have unfriended or people who have unfriended you. The downside of this app is, it will only tell you the people that have unfriended you since you started using it.