Facebook icon disappeared

Solution
It could have been deleted from the home screen, moved to another screen or even combined with another icon that you would have to then tap to view the individual icons it is harboring.

I would check for all those first. Then, if it still is no where on any home screen, tap and hold the background of any home screen and you should get the screen that allows you to choose icons and widgets and what screen you want them placed on. The apps/icons are usually in alphabetical order, so it should be easy to locate.

Now, if by some chance it is not there either, then the app may have been uninstalled. If that is the case, you would have to reinstall it.
It could have been deleted from the home screen, moved to another screen or even combined with another icon that you would have to then tap to view the individual icons it is harboring.

I would check for all those first. Then, if it still is no where on any home screen, tap and hold the background of any home screen and you should get the screen that allows you to choose icons and widgets and what screen you want them placed on. The apps/icons are usually in alphabetical order, so it should be easy to locate.

Now, if by some chance it is not there either, then the app may have been uninstalled. If that is the case, you would have to reinstall it.
 
Solution