Not sure if this was said, but when you said "stray bullets" I thought it was going to be something about accidental discharges.
I actually first thought of this quote by opposition of National Park carry:
allowing loaded and accessible weapons in national parks would create a dangerous environment for millions of American families who annually visit our national parks expecting a safe and enjoyable experience — not loaded firearms and stray bullets
Anyways, yeah I've washed a 9mm cartridge once (which still fired, which surprised me since it was just WWB), and I occasionally would find .22 cartridges around my old truck from shooting sessions. I regularly find empty .22s here and there, from them bouncing into my range bag / rifle case, or into my car. I had several .22 cases stuck under the vent behind the hood of my old Samurai, and I don't remember if I ever got them out before selling it.
But, I really don't worry about it all that much.