This is tricky. First of all I think that it is perfectly understandable that you would be angry at him. You needed him and he wasn't there. Even there wasn't something he clearly did wrong, you still needed something and he wasn't there to give it to you. And that sucks. You have a right to feel angry and sad about it.

The question is what should you do about it? I really think it could be helpful to you if you talk to him rather than changing therapists right now. Working out problems with a therapist can be very helpful. I wouldn't come at it blaming him exactly. I'd focus more on your feelings about the situation. Did you feel hurt? abandoned? like you have lost some trust for him? And is there something you could do in the future differently to convey that the need is urgent?

Also, if he is not available and you are in crisis is there someone else that you could talk to? Some places have an emergency therapist on call that can help with some of that. I think you could reasonably expect him to help you come up with a plan in case it happens again.