Facebook will never intimate you when one of your friend remove you from his/her friends list. , but here is an application that inform you when ever such action take place
The Login behind is simple, After we authenticate this application in facebook and twitter. , the application will take list of friends/followers in a daily basis and cross check on a daily basic with yesterdays list and sends us the difference when ever some difference occur
The application link https://www.twentyfeet.com/ ( Twenty feet ) .
Add services as desired ( twitter and facebook ) and follow on screen instructions
and keep informed