Yeah, the Qantas Pass is just a UATP card that can only be spent with Qantas. Of course, it's possible that it wouldn't have worked on the non-AU Qantas websites, but I believe it would given this comment in the T&Cs which imply it supports other currencies
Of course, I still think this is somewhat Qantas' fault given their instructions (from what I can find) all state you must select "Qantas Pass" on the checkout screen, which isn't really true for non-AU websites, but unfortunately I doubt you can get Qantas to let you retroactively use your pass (and even if they do, the manual process will likely break DSC and you'll have to chase that up)