Just because I'm often jumping from machine to machine, to truck and back, I carry about four different key rings with the basic Cat, Kobelco, and Case keys on each, and then a couple of them have several truck keys, fuel tank keys, and tool box keys on them as well. There's probably the better part of a pound of keys in my pocket any time I'm not at work, so the chance of them getting into the washing machine is pretty low.
I sometimes help out a friend of mine, and I'm really not comfortable with his habit of hiding keys in the machine. Not long ago, two days in a row, I found his right hand man had left keys in the ignition of everything all night, not even bothering to hide them. I told him the story of friends of mine back in school, who grew up in a new subdivision where there was still work going on. (We're talking the 60s here.) They'd gotten a track shovel started, and moving. It ran in circles all night til it ran dry. I suggested that if that kids haven't changed that much, and one could get hurt or killed. Hopefully, he's stopped leaving them that way.