Visa problems Thailand, please help?

Okay so here's my problem. I obtained a 60 day Visa in the UK before coming to Thailand. I only just noticed yesterday that when coming through Thai immigration at Suvarnabhumi Airport (Bangkok), that they've stamped my Pport as 'admitted until February 14' which would make it 30 days from arrival in Thailand. This is clearly a mistake made by Thai immigration and there are no immigration offices open where I'm staying until tomorrow morning. Do I need to leave Thailand and make a border run or will I be able to just stay in the country and obtain another Visa tomorrow? Please if anyone could help I'd be really grateful, I really need to know because I'll have to get a bus to Laos tonight if I cannot stay.