My therapist usually gives me a few months notice as well. Sometimes I choose to be away as well during that time. I regard our sessions as a really important part of the way I take care of myself every week, and I need to plan how I'm going to compensate for that if he's not available. I think it's very important for some clients not to be surprised by things like that.

I'm sorry your therapist screwed this one up! I hope she will learn from it and plan better for you in the future.