Pucci may correct me, but, I believe that there are around 9,000 of us on Longhaul at LHR for BA. So it's quite rare for us to work with the same crew again, never mind see the same pax again.
I have, however been recognised by several pax on my flights and I haven't necessarily remembered them. (I'm not being rude, there's about 300 of them and about 15 of us!!)
Some have been on several of my flights within a short space of time. (Most notably, Robbie Williams 3x in 3 weeks !!! And, no, I was not stalking him!!)