A study conducted at the University of California found that mindfulness meditation may adversely effect our memory.
Participants in the study were divided in two groups; one was guided to mediate by concentrating on their breathing (mindfulness), and the other was allowed to let their thoughts wander (mind-wandering). Both groups were shown a list of words and later asked to recall the words they had seen.
It was found that the group that had engaged in mindful meditation was more likely to falsely recall words they had not seen. The experiment was repeated with three different memory exercises, but the results were the same.
Brent M Wilson, first author of the research paper, feels that mindfulness meditation affects people's ability to determine the origin of a given memory. Our memory has two sources - internal and external. External memory comes from experiences, while internal memory is borne from our imagination.
So, going by this study, despite mindfulness meditation's many benefits (relieves stress, increases concentration, lowers depression) you may end up with no recollection of your session.