I had a friend who described this exact same thing, I obviously thought he was making it up, since I don't remember 99% of my dreams and experience dreamless nights most of the time. I know about REM state and how everyone dreams, so I know I dream but simply don't remember anything, only thing I can sort of pick up from the dream is whether it was a happy one or a unhappy one. I guess this thing you describe must have a name, can't be a coincidence.