I have a different but similar experience: I'll occasionally have a dream, and when I wake up it'll feel so much like I had it before, but as I become more aware I realize I never recorded a dream like that, and it's hard to believe at first that I didn't. I'll often even "remember" things that I've done in the previous occurrence of the dream that I didn't in this dream.

I can't rule out the possibility of actually having had the dream before and just forgotten it, but I have no way of verifying it. Also, I suppose that dreams can simply invent memories which can be confusing. So dreams like that are kind of weird. But this has happened quite often in the past, and so far I've never recorded duplicate dreams in my journal.