Mine would occasionally say something like "I thought of you the other day." And of course if they have to answer an email, or when they are preparing for session.

So, yes, I would say when something reminds them of me fits best.

But I don't know that that means they don't care. It's just that the therapist plays a unique role in our lives, but we do not in theirs. I have many students and I think of them when reminded of them and I do care about them in a teacher-student context, but if we had a disagreement over something like a grade, we would discuss it, but I doubt I would lose sleep over it.