Welcome to Flyertalk Shahar, and welcome to the BA board. I hope you can find this and other threads useful and I would encourage you participate further here.

I'm certainly a buyer of various UP fares and I don't recall anything strange happening with them along the lines that you have experienced.

Just to clarify, and rule out other lines of enquiry: did you simply buy a ticket in First on AA.com - you didn't respond to an email or kiosk uprade offer - and you then flew on their aircraft that you were originally booked on? In other words there were no changes to the flights after booking?