I've actually just gotten off the phone with an agent and he was able to find the flight in question, but he said it's coming up as being bookable as a new booking but can't be added to the OWA, as 'sometimes airlines allocate flights that can only be booked as a new booking'. He's going to get the support team to have a look at it and call me back. I don't hold out a lot of hope though. But it should be able to be added, right? There's no such thing as award seats that can only be booked as a new PNR?