My primary computer is my laptop, which I use at work all day, and then, more often than not, use all evening at home. Last night as I was shutting up shop for the night, I powered down the computer and started putting all the little pieces away. This includes putting my computer and the mouse in my computer bag, as well as tidying up the power and network cables.
Normally, I fold up the mouse cord and take it and the computer to my bag at the same time. Last night, though, two things were different: I wanted to put my cellphone on the charger, and I was in the middle of a conversation with several folks while I was doing this, dividing my concentration. I believe I took my phone and the mouse at the same time, because when I went back for the computer and put it in the bag, I noticed that the pocket where I store the mouse was empty, and I didn't have the mouse in my hand.
I looked. And I looked. And I looked. I hadn't left an area of roughly 50 square feet during the entire time, but nowhere could I find my mouse. Nowhere.
Maybe I've got a cat hiding somewhere around the house.