Have come close twice.
Worst one: I had been carrying a j frame Smith in a pocket for nigh on twenty years, second nature, carried it everywhere along with my keys, phone and wallet, put it right next to me when I slept every night. The morning after visiting out of town with my then wife - no revolver.
Looked everywhere, it was so routine I could not remember laying it next to me, we had gotten home very late. The last time for sure I knew I had it was in a McDonald’s 150 miles away. The only time I had gotten out of the car at all after that was to take a leak by the side of the road 60 miles out and in my own driveway.
Felt like absolute crap, what if I had somehow left it in the McDonald’s? Didn’t seem possible. Dropped it in the driveway? I would have realized I didn’t have it when I lay down that evening.
Called in sick that day, backtracked to where I had stopped to take a leak, looked all around in the roadside weeds nada. I checked Police reports online in the town the McD was in. Nothing.
Made me ill not knowing if some kid or thug had it somehow. Three months later it turned up in a pile of blankets in a closet in my house. HUGE relief.
