I lost an Ego battery for six weeks before it turned up. I was convinced I had it in my lap when I took a nap in my recliner. I searched every inch of that chair several times, upside down and sideways. I shook, jolted it, reached my hands down deep into it... all to no avail. So I searched the rest of the living room, under tables and sofas, convinced the cats had stolen it for a toy. Finally gave up and ordered a new one.
Then I found it totally by accident. I was getting ice cubes and something black caught my peripheral vision up high. It was lying on the white rubber seal along the top of the freezer door, where it had apparently been securely nestled for weeks after I stood it up on top of the fridge. It apparently fell over and rolled into the crack at the top of the freezer door, and for all the dozens of times my wife and I had opened that door, it was snugly settled into that groove up there and never fell.