My observations suggest that there is some problem with Alfred opening Launchpad.
When I open Launchpad from Alfred, there seems to be around a 50% chance whether typing to search and the escape key will work. I can’t see a clear pattern in when it works or not.
When I open Launchpad from Spotlight or the Finder, typing to search and the escape key work correctly every time.
OS X 10.10.3 (14D136)
Alfred 2.7.1 (387)