Happy new year to you too thesunjet, and thank you for your positive contribution to my dilemma.
I found the negative responses interesting, as my main concern was to alert others to take care. Not everyone was negative, and at least I realised that I was not an isolated incident as it had happened elsewhere too.
I will never know if I somehow made a mistake after 20 years of booking on the AA site, but am convinced that everything went exactly as with all of my previous bookings, so the probabilities are with me.
I will contact your suggestion, if for no other reason than to alert them to a possible loophole, or do I mean black hole, in their system.