Originally Posted by
KARFA
Sounds very weird. The whole trip gets ticketed at the start, you don't normally have a separate ticket for the outbound and inbound legs, and the inbound doesn't normally get ticketed after flying the outbound.
Originally Posted by
CraigWatson
A second PNR is possible, but unlikely - we haven't changed any aspect of the booking since paying.
While it's unusual to have separate tickets for the outbound and inbound flights of a trip booked all at the same time, I've seen this happen when a change has been made. But if the OP hasn't made any changes, then it is indeed strange. If paid seat selection was never available for that flight, it sounds possible that the inbound half of the trip was never ticketed.
One question in my mind: although both flights are BA-operated, were they both booked on BA flight numbers?