Never. Never lost my keys or wallet, and never locked myself out of my car or house.
Last year, wy wife locked herself out of the house and then realized she didn't have the keys to the car either. She had to haul ass to get to my oldest son's school in time to pick him up, and then they had to walk back. He's says "errr....where's the car." She says "be quiet."
They traipse home and wait on the steps for me (no cell phone either).
Soon after that we implement the hidden key trick. Oy.