Visa Deadline

My flight changed its flight time so instead of the night of the 27th I'm leaving the morning of the 28th. Problem is mine expires on the 27th (11:59). If I go to the airport at 11:00 PM on the 27th can sit in the airport lounge am I in the clear? Since I already 'left' the country? Or will they stop me at the gate again? If anyone has experience I'd be relieved since otherwise I'm taking a quick trip to Mongolia and right back to renew it.

Also:
I don't have time to apply for an extension (tried) and their transportation administration told me it was not their problem (which is true).