App icons go missing on MacBook
How to Rebuild Launchpad Database in OS X Yosemite (10.10) and Later


Go to Library folder, which is hidden. To access it, click anywhere on desktop and make sure you see word 'Finder' in the top menu near Apple logo.
Press and hold alt/option key and in the top menu bar select Go and finally Library.
In the Library folder, locate and open the Application Support folder.
In the Application Support folder, locate and open the Dock folder.
You'll find a number of files in the Dock folder, including one named desktoppicture.db, and one or more files starting with a dashed set of capital letters and numbers and ending in .db. An example file name is FE0131A-54E1-2A8E-B0A0A77CFCA4.db. Grab all the files in the Dock folder with the dashed set of letters and numbers that end in .db and drag them to the trash or press ⌘/command + delete keys.
Launch Terminal, located in the /Applications/Utilities folder.
In the Terminal window, enter the following:

defaults write com.apple.dock ResetLaunchPad -bool true; killall Dock


Launchpad has now been reset. The next time you open Launchpad, the app will rebuild the databases it needs. Launchpad may take a bit longer than usual to launch the first time, and the Launchpad display will now be in its default organization, with Apple apps shown first, and third-party apps next.