I had several sessions with a T whom I had seen for an extended period of time about 10 years previously. I was surprised to discover some of the memories she had of my time in therapy with her, and it was interesting to see that what stood out for her was very different to what stood out for me. She didn't remember some things that I thought were pretty important (and 'should' have been remembered) but other things that she viewed as quite pivotal and important *I* didn't remember until she raised them.
I doubt that I could muster the courage to ask a current T about what was memorable for them - like others I would worry that I was putting them on the spot, and that nothing was memorable!