Most people remember everything that went on while they were in hypnosis, but sometimes, if they went into a particularly deep state, they may forget what happened. Sometimes the therapist will suggest that the client forget what happened (with the client’s consent obtained prior to hypnosis), and they do. Other times people have the misconception that they are supposed to forget everything, so they do – because they gave themselves the suggestion to forget!
In any case, your unconscious mind will remember the things that are important to you.