I hope you feel better today and your session goes well.

I would be startled by the forgetting too. Not only would I be very disappointed to miss a session, I think for me, it would make bring up a huge fear that my therapist would interpret it to mean that she/therapy isn't important to me. Even though I can imagine her dismissing it as just a human thing we all do - forgetting or getting even important things mixed up.

It's so understandable that you had your regular day - Wednesday - in your mind as your next appointment day.