Why even have a backdoor if there's no working lock seriously just leave it wide open.
Your dog wouldn't bark at an intruder? Man I have two of the sweetest dogs you'll meet a Pitbull and a Boxer but the one time someone tried to come in the front door they regretted it.. my opinion next time you have a dog, train them to not like gloved hands and masks.. it's what we do lol.
I'd have to say I was in a similar situation when my parents went to Chicago for a week home alone with just the dogs. It turned out I sleep walk, which I actually knew but I couldn't figure out why doors were closed or things moved. I do it all the time and I don't know why but for some reason that time I was too nervous to realize it. The combo of the additional stress + junk food(I'm not as good a cook as my mother) and such made me sleep walk a bit more often. You could be sleep walking and doing things, ever do it before?
Edit: If all else fails take your dog in your room and anything very valuable and lock your bedroom door hide under your covers and yell "go away boogey man!" He's going to eat you.. he wants your skin and your things he's coming!!!
Edit: Omg the back door!!!! there was a knock.. ahhh!
Yet another Edit: I'm messing with you relax your imagination is running away with itself because you're out of a typical pattern.
