there's heaps of discussion of this in the oneworld award thread. But to summarise:
Whenever you make a change to an award booking, such as by adding a flight, the booking needs to be re-ticketed (receiving the itinerary in your email indicates the booking has been ticketed).
Until the ticketing takes place, every leg of the journey (including those previously ticketed) could be cancelled out by the carrier. Qr are notorious for cancelling out unticketed bookings. I've had them cancel out previously ticketed flights within 4mins of a change to the itinerary!
Moral of the story is whenever you make an amendment to an award booking, especially with qr in the itinerary, stress that it needs to be ticketed asap. If you don't receive the itinerary in your email within 24hrs, call again until it is. Many of the qf agents don't even know of the problem with qr and so will often just leave the booking in the slow ticketing queue which means it won't be ticketed until a few months before your journey. If that's next year, you can guarantee you will lose some of your flights between now and then.