Sounds like a total customer service failure by BA. These days it seems that aside from First and perhaps business, it's a race to the bottom even on legacy carriers. Two summers ago good ol' Lufthansa managed to lose my bag inbetween two short-haul flights. They did inform me as soon as I landed (by text) that the bag was 'elsewhere', but it took 3 days to get it back and not a little stress. The AirTag inside provided an interesting visual narrative.
Back in the 80's I was flying from HNL to LGW with World Airways (if anyone remembers them). We flew HNL-OAK-BWI-LGW. All went well until my bags went on the FRA flight instead. Once alerted, they put a 'RUSH' notice on my bags and Air India had a flight to LHR leaving shortly after. Sadly the bags went to DEL on the opposing AI flight and it took 3 or 4 days to come back home again.