Some /system/app disappear on app drawer! How to start an app not in drawer? Android 4.1.2

Somehow the original Home launcher icon disappeared after OTA update, I'm not sure if it's the only app that disappears, but it's the most obvious when I'm testing other launchers.

It's registered as a launcher app, so if I unset the default launcher, I can choose it.  But I'm not able to call it in App Drawer, or shortcut->application.

I wonder if wiping the dalvik cache helps?

Anyway, I'm looking for work around like running a shell script to start the app or switch to it!

Is there a file which contains the list of apps for App Drawer?
If you replaced the stock launcher with a 3rd-party launcher, the only way to go back to stock launcher is to clear/unset the default launcher (which is what you did), and select a new launcher - in this case, the stock launcher. You will never find a shortcut to the stock launcher in your list of apps.