So they were not looking for bumps? That must have been a lightly booked flight!
Two years ago I was booked on a 747 ORD-SFO with an upgrade confirmed to Business, and we got swapped to Ted the day before. Since the flight was oversold by over 150 people I was proactive the night before and called reservations. The very nice agent gladly rebooked me on the next international 777 in three class F!^ I was still at the gate to see the Ted boarding chaos, and there were some unhappy campers!