What happens overnight in a bookstore?

Arriving at the bookstore on a chilly Sunday morning my thoughts turned to warming the place up before opening.  I was thwarted in this as the heat-pump's vital round "ON" switch had done a disappearing act. It was there when we closed up yesterday, but had vanished  into thin air overnight.  Maybe it was inspired by our travel books to go on a journey of its own?   It was eventually located under the depths of the false floor of our display window, having been on a bit of a drop and roll adventure overnight.