After a fruitless search for the battery I decided to pack it in and make dinner. While standing at the stove I watched Little Guy carefully open one of the bottom drawers and poke a Hotwheels car down the side of some dishes in there. I had a light bulb moment and opened the dishwasher. There on the bottom lay the battery. Yippee. It won't need to be fingerprinted. I think I can say with 100% certainty that none of the other family members would hide something in there.
I'm somewhat concerned about his sneaky track-covering. Replacing the camera to it's proper location AND locking the dishwasher. He's only two years and one month!
I'm in a better mood now :)