If you implemented a home screen replacement app, your app should be set as the default launcher/home screen.
setComponentEnabledSetting()
allows you to override the intent filters in the manifest and essentially disable them. It sounds like he overrode the filter for the launcher intent after the user unlocked so he could get the default home screen to show up.
That being said, I don't recommend writing a lock screen replacement, there are too many issues, it's hacky and insecure. Focus on lock screen widgets.