My wife was a sea kayaking instructor, and she'd always take the ring off before class. Sometimes she'd forget to do it at home, so she'd leave it in a hidden spot in the car. Sometimes she'd forget about it and not put it back on until the next day.

One fateful day, a car wash and vacuum happened in the interim. Most likely it got sucked up in the vacuum and is now sitting somewhere in a dump, or in a seagull's gullet.