Two things: Molly has put on a few pounds over the winter (haven't we all?) so I loosened her harness. Apparently, I loosened it too much:
We got a lot more snow again yesterday and the piles at the end of the driveway and along the street are so high it was impossible for Tom to see whether it was safe to back out. He texted me to come out and direct traffic for him, so I slipped on my shoes and ran out. Without putting Molly away.
Not a good idea.
When I had Tom safely on his way, I came back in and all looked normal. Molly was standing beside my leather chair, next to my computer. Nothing seemed awry until I reached for my wireless mouse.
I've looked and looked and I can't find it anywhere.
Found it! She put it in her toy 'pot.'
(we keep Molly's toys in an old enamel pot--she chewed the cute little basket that we kept Ivy's toys in)