What could be the reason for dock icons to have disappeared? So this has happened to me again, my icons from desktop and the icons on dock and launchpad have been disappeared. I'm guessing that the icon builder daemon has crashed. 

What should i do to get back all the icons to back where it was?
That is a strange behavior which happens to many users. One way to fix that is to open a terminal and use the killall-command.

Because the launchpad is connected with the dock, you can just use the following command to get your icons back:

killall Dock


That should fix your dock and launchpad-problem. But I don't know if it will help for the missing Desktop-icons.