Dear CgCookie,
Last lesson we added a grenade to our weapon this lesson you don't even have it in your game, what happened to it?
From Ivan.
Each lesson is packaged up based on what was included with it. Since the grenade was only used in one lesson there's no reason to include it later on. You're free to import later lesson packages which will add to your current project files. If you import each scene individually then you'll get what is needed for that lesson.