I think a better analogy for this sort of thing is an unknown location. It's like you took some unencrypted text and hid it in a tree in a national forest. Eve

I think a better analogy for this sort of thing is an unknown location. It's like you took some unencrypted text and hid it in a tree in a national forest. Everyone strongly suspects that the unencrypted text existed in the past. It's just that only one person knows how to access that text in the present. The problem with the locked box analogy is that it implies that the cypertext is in some way equivalent to the plain text. In practice that isn't really true. If you don't have the key you don't actually have the plain text. Nothing says you can't look for it if you want. You could even hire a company to help you look. Can you force a company to look if that search would be against their business interests?