couple of thoughts, one I know darn well when my T locks her office at the end of the day she leaves all her clients "in there". Even if I were to bump into her on the sidewalk as she was leaving I would be "just me" she would have no thoughts bout our therapy together. To me it is part of having healthy boundaries as a T. If it is uncomfortble for you I would call him and ask for a "session" where you two could talk about it. This is not something you had known was going to happen when you worked with him or even when you ended therapy. Having a conversation about it IMO is important. Personally, for me, I would feel best asking for that conversation to happen in his therapy office rather than office hours as a prof because it is an emotional topic.