I don't wish to hi-jack the thread, but I have eactly the opposite problem.

I have booked an itinerary with BA which also contains a flight with AA. I cannot seem to find the AA booking reference anywhere, I tried on checkmytrip.com, finnair, etc. etc., but nothing. When I try to select seats using the link on MMB, I get an error message, saying that the reservation is not available on AA.com. Needless to say, using the BA reservation on AA.com brings nothing.

Any help gratefully received!