I don't think it's that outside the norm of human experience to wish someone who has hurt us was dead. I don't get why therapists can't see the nuance of that feeling. Recently my therapist suggested that I had probably wanted to kill my husband a time or two. He knows I'd never actually do it, but is aware that the thought must have crossed my mind, and he was correct. He did not make me feel ashamed for having those thoughts. Are these other therapists so sheltered that they've never wished harm on someone else? Personally, based on her reaction, I'd look for someone else.

I believe if you state intent to hurt someone, or yourself, they have a duty to warn.

However, you did not state any intent to harm but said you wished X. Personally, I think that T was a bit extreme. Not only because there was no intent to harm, no plan... but you also don't even have a clue where your ex currently is.

It's up to you to go back to this T and make it clear that you did not threaten to do anything to that ex and see how they react and whether to stay with them. If it were me, I would not stay with them. I would not trust them and would feel I'd need to watch extremely carefully everything I said in case they jumped to the wrong conclusion(s) and 'punished' me.