40 years ago - bird hunting, walking through a never ending series of small identical hills a few feet from the marsh surrounding a small lake. Worked up a sweat and stopped to remove sweatshirt. My (then) wife was along to take some pictures, and somehow dropped her light meter, size and shape of a large key fob, while changing shirt. Walked another hour, then headed for home after completing walk around lake. Discovered missing meter an hour later when got home.
Was almost dark, so went back the next day to look for it. The hills all looked the same, so we searched every one of them. We had searched one more and had pretty much given up, when a large blue racer darted out of the grass. We watched it as it moved between us and crawled right over the lost meter.