I learned the crate lesson with Hope this same way!
I was putting her in the laundry room during the day when I'd go to work and she figured out how to work door knobs and let herself out (she still works doorknobs)...I had an old lamp with the turn-key style on/off switch on a table she knocked over into a corner. The turn-key hit the wall, turned on the lamp and the lamp started burning through the drywall (mobile home too). If the bulb hadn't burnt out my house would've went up with puppy, kitties and all. I actually had charcoal in my wall from the burning.
Needless to say, I got a crate that night. And come to think of it, she was about 6 months old too
Intelligent little stinkers they are.