Once my TA was able to get me a fare on a booking class that CX already stopped publishing fare on for that flight (on a 23rd December SFO-HKG flight about 5 years ago). My father was hospitalised and I was in a rush to get to HKG. (Note: Seat guarantee is useless unless there is a fare.) My new TA called CX to get me a seat. Someone was probably bumped off the flight.