Did you purchase the ticket within 24 hours of placing the fare on hold? Unless you put it on hold at 11:38pm, I would guess not. Note they say they guarantee the fare for up to 24 hours. They'll hold the reservation for longer (I've had some int'l flights hold for 3 days for some reason), but technically they only seem to guarantee the price for 24 hours.

Regardless, they don't have anything programmed into the computer about a 24 hour price guarantee. To enforce that guarantee, you shouldn't call the EXP desk, you should call the web services desk. Many people here have reported in the past (even before they put the language up about guaranteeing the price for 24 hours) that you could call them up and have them restore the old price and you could then complete your purchase online. I think you may even get the 1k booking bonus.