So, over the weekend, two of my flights (paid) vanished from MMB. I have not yet received any refunds/vouchers, but I suspect they are now being actioned.
My points flights for this Thursday, on the other hand, are still showing, plus I am being totally bombarded with text messages about changes to my flights eg my 0620 jet service CBR-MEL has now turned into a 1330 Dash-8 service (arghhhhhh - if I were still travelling, I would not be happy about that). So today I bit the bullet and called Qantas. I am a WP and I got through at 9.30am today in about 3 minutes flat. Spoke to a very patient and helpful service agent in Tasmania - thanks Joe - who did a manual cancellation. I'm grateful for that, but it is odd as I have screen shots that I already cancelled this flight on line at the same time as my others.
So my advice is, if it still shows on MMB, even if you get the "can't find this booking" message, it is probably worth calling them to get it resolved.