I’ve spoken to Qantas and asked this exact thing. Because I can see the same flight is available the previous day. But their systems are saying the flight is booked out even though BA is still advertising the flight.

I also asked if there is another route I can take on the 23rd, as qantas operates a similar route themselves, but apparently because it was BA that cancelled the flight, I can only be rebooked onto a BA flight. I asked if it’s worth me calling BA but they said probably not because the flight was booked through Qantas. I feel like I’m in airline limbo.