That happens more than you might think. Have you ever recalled something from your childhood and thought "oh, man, I haven't thought about that in years"?

Memory produces a lot of weird references and metadata. There are some significant experiences in my past where I'm pretty sure I don't remember the thing itself at all, I just remember remembering it. The vivid, multisensory experience of the event fades, and is replaced by the story I told myself when I thought about it later.