I have never had a dream that was a memory. But in movies and in TV, this happens all the time. It's an easy storytelling device, to catch people up on something that happened off-screen to a character in a movie, or in an earlier episode of a series, so I understand why they use it. But it just always rings very false to me. So I wonder if it was conceived purely as a storytelling device, or if it is actually something that people experience, but that has never happened to me?