I've only had one escape and it was recently. He turned up 2 weeks later near a water and food source. You may want to look in any places that would accommodate his/her humidity need and if you have a pond or even a sprinkler system nearby, be on the look out there. Eventually they need food and water.

Mine turned up in my neighbors yard under their irrigation hose next to their veggie garden which he had been nibbling on.

Regarding winter, I would not put it past the turtle to survive but where you are is quite different than where it came from. Your frost line is likely deeper so ideally you find him before winter.

Fingers crossed.

Paul