Hi Forgetmenot,
It took me a long time to learn to hold onto my T's appearance. And I think it's a combo of disassociation and lack of object constancy.
When we are first learning to stay and not disassociate, we are often highly activated. When you are really scared, the limbic system actually floods your brains with hormones that effectively take the frontal lobe "offline" so that when you're amygdala (whose job is make sure you survive at all costs) screams to do something like "run" or "fight" your frontal lobe won't interfere. It's kind of like a life guard trying to rescue someone who is so panicked that they're fighting the lifeguard. The lifeguard knocks them out so they can get them to safety and sorts it out later.
So you're ability to think is literally compromised. So between activation and actual disassociation you are literally not inputting the stimuli that would allow you to form a memory.
The second factor is something called object constancy, which is basically a fancy term for how well can you hang unto someone when they're not right in front of you. Object constancy is something all human beings need to learn in relationship. When babies are born, they do not recognize a self and other, they believe that they are one with the mother. As they grow and develop, they start to differentiate and understand that they are a different person. But that can get scary because they need the "other" to survive. So when the "other" leaves it can be quite terrifying. It's the reason babies cry when left alone or when a parent leaves. So we slowly teach a child that going away is not permanent by starting with very short intervals and increasing them as they get older. Which is why a 10 year old is usually a lot calmer when a parent leaves, then a three year old is. A really good way to understand this is the game of peek-a-boo. That is often the first lesson a child learns of object constancy. We hide our face, in effect go away, but for the briefest of intervals and then we come back. Which is why a child is often so delighted when playing because it's a warm secure feeling to have the person "appear" again. Eventually we learn that a person continues to exist when they are away from us and that we still exist for them.
For people with insecure attachment, who could not trust that their caregiver would be available, this process can get short circuited. We never learn how to keep a sense of connection or an ability to believe someone is still there when away from us. This literally interferes with our ability to "hang unto" our sense of our therapist being there when we're away.
When I started with my present T it was not unusual for me to spend most of a session with my eyes closed and my face covered. and it was very hard to hang unto him between sessions and that included really remembering him. There was almost a "shock" of recognition each time I would walk in, like "oh yeah, that's what he looks like, of course, how could i forget?" As I healed and my ability to remain present increased, so did my memories of my therapist and my ability to hang unto the connection in between seeing him. It helped that my T has a relative who posts a lot of family pictures on the web, so I had pictures of my T to look at in between which was quite helpful. Now that I can really trust the connection and have a very strong sense of him being there at all times, I also have a very rich mental sense of him. I can recall expressions and gestures and the sound of his voice very clearly.
So what you are experiencing sounds normal to me, and I believe it will improve as you learn to both trust your therapist and trust that she will continue to be available.
AG