You mentioned paranoia - which occurs with Bipolar. As you have already considered it I would encourage you to explore this possibility further.

I see absolutely no reason why a psychiatrist would do this. Doing so puts their entire career at risk. Would he really do so?

I have been taped, but I was participating in student learning - and was advised it may be used for training purposes. I firmly believe my own psychiatrist has never done so, although twice he asked if he could talk about the session with a colleague.