Which makes me think of three things from my own life:
When I was in fifth grade or so, I read a great library book called The Towers of February, by a Dutch author named Tonke Dragt. It was about a boy who wakes up with no memory in another world. I loved it, so I went back a little later to check it out again. The library had no record of the book having existed. It wasn't on the shelf or in the card catalog. It wasn't in Books in Print, which at the time I thought meant there was no record of it having been published. I spent something like fifteen or twenty years looking for the book, in bookstores and libraries, but nobody had ever heard of it.
And then along came the Internet, and I found and bought a copy online. It really did exist!
- Sometime in the early '90s, I started having vague memories of a TV show about a white lion. I remembered having seen it as a kid, which was a little weird because we didn't have a TV for most of my childhood. But I had never seen or heard of any indication of it since childhood, and nobody seemed to know what I was talking about. Then The Lion King came out, and there were eventually articles about the possible connections between that movie and an anime TV series called Kimba the White Lion. Which was, sure enough, the show I remembered.
At one point in college, I checked out a book from the town library. I think the book was Summer of the Falcon, by Jean Craighead George, which was another book that had disappeared out of my awareness and memory for a long time. I think the library got it via interlibrary loan. When I was done with it, I took it to the library and returned it, setting it down on the check-in desk.
A while later, I got a notice from the library saying that I had never returned the book. I told them I had. They told me I hadn't. I had an impassioned fight with them on the phone about it. I felt that my honor was being impugned, that they were calling me a liar. I refused to pay for the book, and they revoked my borrowing privileges.
I was angry and bewildered about that for a long time, but felt pretty self-righteous about it. Until the day came when the library let me know that someone claiming to be a friend of mine (naming me by name, but not giving their own name) had returned the book, months after it was due.
I still have no idea what happened. I think that I must have loaned the book to a friend (though I don't know who) and then forgotten I had done so, and created a false memory of having returned it. But the memory of returning it was very clear in my head.
I suppose it's possible that I left the book on the counter and a friend of mine who had seen me do that immediately and sneakily picked it up and walked out with it without telling me. But it seems much more plausible that I just misremembered what happened.