It has to do with the way your brain and memories work. PTSD, research what all it encompasses and then it should make sense why you don't remember at the moment. I know the longer I have been in therapy the more memories I have recalled. It is a slow grueling process, but it can happen. Ask you therapist which diagnoses benefits from hypnosis they will let you know your options. I'm strapped for cash and lack insurance but I would love to get a therapist that uses hypnosis to bring forth alters and safely revisit traumas, since I have Dissociative Identity Disorder as well. I think hypnosis is also good for addiction and stuff as well.