OP was ticketed to MEL, not to HKG and nobody looks further than the most efficient routing to MEL on any carrier with an interline agreement. If QF was that routing, it was not a "screw-up" either by human or computer.

For those who wonder why BA does not notify passengers when it knows bags are delayed, it simply lacks an automated system to do so. The notion of having staff send individual text messages about bags around the world is simply not commercially viable.

The technology, of course, does exist. AA's app shows every bag and tracks it from the time it is scanned at check-in, onto the aircraft, off and to the delivery belt or handoff to another carrier. It relies on the same data feed AA uses for baggage manifests and is exactly what agents see if you speak with one. Thus, fewer panicked calls and if one arrives to see that one's bag did not make it onto the flight, one need not wait and may head straight for the baggage office.