It might be just reconstructive memory. Not all of your memories are complete accounts. You might remember a part of the dream, but the events have effected how you remember it.
When studying psychology at AS level our psychology teacher tried to replicate the 'War of the ghosts' experiment, which essentially demonstrates how reconstructive memory works.
Here's a brief summary of what I'm on about:
http://www.bookrags.com/research/reconstructive-memory-lmem-01/
From there:
Quote: "
Subjectively, memory feels like a camera that faithfully records and replays details of our past. In fact, memory is a reconstructive process prone to systematic biases and errors—reliable at times, and unreliable at others. Memories are a combination of new and old knowledge, personal beliefs, and one's own and others' expectations. We blend these ingredients in forming a past that conforms to one's haphazardly accurate view of oneself and the world."
Think of it as your brain filling in the blanks.
Or at least I think it could be to do with reconstructive memory, I'm not a psychological expert (I'd hardly call an AS level 'expert') or anything, it's just an educated guess.
Maybe this will help you feel a bit better about your dreams.
Alternatively you've got a case of Nicolas Cage syndrome. (as mentioned.
)
But I hope your sister is okay.
