What happens to the batteries that vanish in the night?

Have you ever noticed that there seems to be something that eats batteries? No, I don't mean as in a flashlight that uses them up reading under the covers of a child's bed, and I don't mean that video game that consumes more double A's than one can reasonably expect it to. I mean there is something undefinable that just seems to... eat batteries.

As I get ready for winter I am looking around and realizing that we need a lot of batteries in the most unexpected places. One of the cars outside seems to have lost its battery - no one knows where to though. The door on one of the smoke alarms stands open, a clear indication that the battery eater found the backup battery in that smoke alarm and ate it. My flashlight is missing batteries... and... why does my old watch not have a battery in it? What possible use could any battery eater find for that tiny thing?

I had never thought to shop for batteries online before, but I was browsing Interstate Batteries and realizing that they are a lot cheaper than the ones I can get anywhere locally. Maybe I'll just add battery shopping to the list of online shopping I want to do this fall.