Slight thread drift, but,...
....I usually put my house/car keys in my checked baggage, because I have a pocketknife on that ring. Occasionally, I do find myself in town with no luggage and therefore no keys. So I've been there and done that. He might have been in a similar situation.
Uh, wouldnt it be simpler to take the knife off the keyring and not take the chance of not having your keys?
I dont think I'd care to be without keys, depending on the airlines to get the baggage there on time and the right place.