Numbers has stopped showing up in Launchpad
Just type your application name in Launchpad's search box found near the top of every Launchpad screen. The icon for the desired App should be displayed on a new screen by itself - click and drag it to the desired location in Launchpad.

A commandline call may help as well - but be warned that it'll rebuild the Launchpad from scratch and will remove  any customizations you've added:

 rm ~/Library/Application\ Support/Dock/*.db; killall Dock