This happened to me last week, LCY-EDI.

Wife got some good news at work, and £65 for an extra 30/35 TP seemed worth it. We were on separate tickets, so had both phones out doing the upgrade at the same time. Our respective BA Amex cards were charged. No problem checking wife in but no boarding pass, I couldn't even checkin.

Agent at the airport said there are no seats for me (sorted the other boarding pass) and I'm now stand by for CE or back into Y. A little huff, over to reservations and some nice lady seems to have moved the curtain (1 hour before the flight?) and popped us both into row 6 (with 6CD empty).