2 hours after checking in for tomorrow's return flight, I get a message that it's cancelled. No rebooking options available, and the Platinum Service Line is basically unreachable (I managed to get through after at least 20 attempts but gave up after being on hold for ages).
I am now in possession of a train ticket for tomorrow's journey. That's what I get for being too clever and changing my ticket; the flight I originally purchased is still scheduled to operate