I am sorry seeing your T on a date was such a difficult experience for you. I think as patients we know in the abstract that our therapists have S.O. and a personal life, but it is different to see it.

I think that what their therapists think about their significant other is independent of what they think about us. For example, I love my husband but it doesn't prevent me from caring/liking other people.

I also know what you mean about hard it is realizing (or at least believing) that a T would never be attracted to you. My T is a straight woman (I'm female), so I know she would never harbor any sort of romantic countertransference.