Looks like my theory about the shoe bat was probably correct. That was, one of our dogs probably carried it into the house and lost it some time before MizBubs noticed it.
I got home from work tonight, ending a long week. Within minutes of arriving home I was greeted by the sound of my youngest daughter shrieking at the dogs. A badly injured little brown bat was out on the back porch, apparently just having been chewed on by Duffy. My daughter was upset. I found out that the town we live in does not have an animal control officer. I also realized that the course of action I would have taken if alone--quickly severing the bat's head with a shovel and putting it in the garbage--was definitely not the thing to do under my daughter's bat-mourning gaze.
So that's how I came to be standing on my driveway at 9:30 at night, duct-taping a garbage bag to the exhaust pipe of my car, euthanizing a bat. I hope the neighbors saw this. And to really top off the whole effect, I wore a headlamp.
I have to go to sleep now. In the morning I have to take bat remains, on ice, to an animal hospital to be tested.