If you haven't made any changes to the building (sealing cracks, etc.) it will find its own way out. They don't need much room to get in and out of buildings. If you don't mind having a hibernating guest for the winter, just let it be. It will leave when the weather warms up and the insects come back. If you have any issues as it gets time for the bat to be on its way, just e-mail me again.