Call animal control asap and get away from the bat! They're an extremely high risk species for rabies and if it's not flying with the rest of the bat colony, it may be sick. I'd open a door on my way out, if I was you. If it can't find its way out then with it's echo location, it probably is sick.
We have some big bat colonies in Austin and I used to work in the Animal Shelter and almost every bat they brought in had rabies. I try to stay well away from any lone bats. I like bats a lot; they're great, interesting, and beneficial animals but the rabies threat scares the heck out of me.
ETA: Forgot to add that here if you even pick up a bat (and don't get bitten) you still have to go through the rabies shot series. I think it's because they groom themselves so much and there's always a good amount of saliva on their fur and skin.
