I'd suggest that you ask him. I suspect that he wants to help you to get to know all the parts of you. So, he will want to share whatever happened when the time is right. I'd be pretty curious about that.
Besides, my regret with my last T is that I didn't ask her what she had ask me before I zoned out for a second and forget what she'd ask me. I just remember her asking me something. Then, I started having my thought swirl around in my head and then she ask me why I was acting weird? I said that I had no idea and chickened out of asking her what she's ask me before that.
Also, I don't think you had a "disaster." I think it might have been scary to have noticed the odd change and lack of memory. However, the mind can do strange things. That's why we talk to Ts. So, when our mind does a strange thing in session, it is not a "disaster." It just is what our mind did.