Bought the game today, played for about 4 hours, built a beautiful 2 story house in the sky and thought all was going well...
Turns out, it wasn't auto saving like I wrongly assumed it was. I was retreating into my house during night time which had been safe from zombies the every night prior and an exploding zombie was on the second floor of my house and pretty much destroyed everything I had worked on.
Went back to the main menu to re-load my save, turns out there was no game to load because it wasn't saving and now I have to start all over again.
I didn't have torches in my house because I was unable to find both ingredients for it. Could that be how he ended up in my house? There was only one path to get into my house, which was highly elevated off the ground, and a trap door that should have stopped it.