So you felt like you were doing your mantra for about 2.5 hours? You might have lost track and drifted off during that time and just can't recall the dreams. I have had a feeling of being awake for a long period but then remember a dream or two and realize that I did get to sleep, it's just the state before going to sleep felt very similar to when I woke up from the dreams and just did not remember the dreams at first. Good luck with dream yoga as well. Sivason is the man! :)