Launchpad is OS X 10.7′s iOS-like app launcher, it’s a nice utility but it does have some quirky behavior in Lion. One of the major issues is that sometimes apps won’t appear in Launchpad at all, or when you delete an app it doesn’t disappear as it’s supposed to. If you run into this, try this tipleft in the comments about LaunchPad Control about refreshing Launchpad and its contents.
Launchpad is attached to the Dock app, so the easiest way to relaunch LaunchPad is to kill the Dock from the command line:
Both the Dock and Launchpad will relaunch and that should clear up most minor issues with app persistence.
Refresh Launchpad Contents
If relaunching alone hasn’t fixed LaunchPad and apps are still not showing up, try deleting Launchpads database files located inside your home ~/Library directory, which forces them to rebuild. The directory path you are looking for is:
The fastest way to get there is by using Command+Shift+G in the Finder to access the “Go To Folder” function, then just paste that directory path in. You will see a folder like this:
If you want to back these up you can, otherwise just delete them by dragging the .db files to the Trash, and then kill the Dock again from the Terminal to force the databases to regenerate.
Take note that you will lose any custom icon placement and folders that are setup within Launchpad, because that information is stored in the database file you are trashing.
One-Line Terminal Command to Refresh Launchpad Contents
If you are comfortable with the command line, you can also do this entire process through the Terminal with the following commands:
rm ~/Library/Application\ Support/Dock/*.db ; killall Dock
If you want control over exactly what shows up in Launchpad rather than just creating a bunch of folders, use the third party System Preference Launchpad Control, it’s free and works as a sql frontend to the Launchpad database.
Thanks to Igo for the tip!