Thanks for the advice and suggestions.

The good news is that the BA baggage line found the receipt numbers, so there are now proper missing bag reports for both of them.

I have Air Tags in both bags - currently one’s at the northern end of T5 behind M+S, the other at the southern end. Both tags lave “lost mode” activated.

CWS - I was in the habit of doing much of what you suggest before the pandemic, but my routine slipped. Lesson learnt.