LEGO Ninjago: Messed up badly

When I got LEGO Ninjago, I asked my dad if he wanted to play. He said yes and I set it up. We played with me as Kai and him as Frackjaw. After a while he won, and I cleaned up the mess. Later, when I was reading the Quick Play Guide, I saw that I forgot to put a BOTTOM PEICE on it!!!!!!!!!!! I told my dad and he laughed.