It didn't touch anyone. It was peacefully sleeping in some dark corner, waiting for the appropriate hour to go ou hunting, or drinking, or hanging with friends - whatever bats do when they are not asleep. And then - we appeared. Heavily walking past, sneezing and coughing, clanking with equipment and loudly chatting. Flashing light to each surrounding dark corner. No wonder it freaked out and attacked us. Next time we should show a bit more respect.
When encountered, Disturbed Bat makes hero hide 1 die back to his bag.