I can hardly imagine how shocking this termination must be for you. You may never know the true reason T terminated. If you decide to find a new T, they can request your records. The answer may be there.

I would want to know...to help me avoid this the next time around.

If that T is sensitive to criticism, you may be better off in the long run moving on to a T who is more experienced.

Did the T give you a referral to another T? Did T offer any termination sessions?
What did T say?