Concur that the system won't be updated that fast.
Back when I first went Gold (1999, believe it or not), my threshold flight was LHR-SYD on BA and - get this - QF had my Gold/Emerald status in their system by the time I arrived in SYD. Took BA until after I got back before they could see it. Bizarre.
Have you tried looking at the lounge calendar, to see if there's an FTer in the airport that can guest you into the lounge on that day?