I had a similar experience a 6/7 months ago.

I was however travelling with my MD and paid for upgrade but he was then unable to upgrade. The offer dissappeared.

We phoned and begged and exactly the same result, no space limited offer etc. There no way I could get the situation resolved.

When I got to the airport, went straight to the ticketing desk and explained the situation and paid for an upgrade circa £300 back from JFK.

The £300 was well well spent in this situation!