It might have been the word "friends" that your T had to say no to. I asked my exT if I could send her emails a couple times of year just to say hi and update (not as friends), and she welcomed that. My exPdoc on the other hand rejected the same request. That really hurt because we had been working together for 5 or so years and then it seemed like she wanted nothing to do with me. I guess it just depends on the person.