Many wildlife rehabilitation centers offer such services, and they all differ as to how involved they want you to be. Many centers will come and take care of the injured animal, bringing it back to their facility. These are referred to as field rescues . This happens often when larger birds, such as hawks and owls, are hit by cars. It is very easy to get it out.
Bats fly into open windows searching for a sheltered roosting spot.
Find the room that it has flown into and make sure the window is still open. Turn out the lights and shut the door behind you to seal off the room from other places in your house. The bat will use its sonar to echo-locate the open window and leave. If you can, wait until morning to check the room again. Constant contact with you can stress the animal into injuring itself.