VegasGambler

The FAs definitely know if you have been upgraded. Different airline, but....

I was once on a long UA TATL flight. Work had paid for PE and I had cleared a miles+copay upgrade to J. Shortly after takeoff a FA came up to me and told me that there was a Global Services customer in a different seat that was broken (would not recline or lie flat) and asked if I would switch seats with him because he paid a lot for his flight.

I thought it was such a strange request. She didn't even offer me anything in exchange. She seemed to think that I would think that because he was high status and he had paid a lot for his flight I should move to a broken seat. Maybe if they offered me the cost of his full fare J ticket....

Anyway I politely declined the "offer". I have no doubt that she asked me because I was the one (maybe the only one?) in the cabin who had been upgraded. As far as I could tell, she didn't ask anyone else. So, yes, the FAs know!

ConstellationClass

IMO you took quite a risk that the FA didn't decide you were "disobeying crewmember instructions" and make life petty and mean for you.