Issue with my launchpad on MBP Retina 13"
A simple Google search gave this article on OS X Daily, which is interestingly based on this Stack Exchange answer. Here are the relevant bits:


  
  Open the Terminal application and enter the following defaults write command string: 
  defaults write com.apple.dock ResetLaunchPad -bool true; killall Dock
  Hit return and wait for the Dock to relaunch and Launchpad to reset
  
  
  When you open Launchpad again, the layout will have returned to the
  default, placing all bundled apps onto the first screen of Launchpad,
  and third party apps onto the secondary (and third, if applicable)
  screens.