You know I'd also feel bad if my T forgot an appointment and I would also experience "everyone does" as dismissive. That sucks. I'm sorry it happened to you.

But unconscionable? Really? Perhaps disorganized. Or rude. Or scatterbrained. Or maybe just human. But I think save unconscionable for truly awful, unethical, malicious or violent behaviour.

It's important to be able to say to a T (or to yourself) "right now I'm so vulnerable that this type of mistake feels just devastating to me."

You can have compassion for your own justifiable feelings of distress without telling yourself that you were severely wronged. In this way you can also learn compassion and patience for the imperfections of others.