Hi, it's one of the small forest bat species either Little forest bat Vespadelus vulturnus or Southern forest bat Vespadelus regulus. If you still have the bat, if you are able to measure the forearm very carefully (to mm accuracy) then we could tell you which species. I can give you some guidance if you're not sure how, also you should wear some gloves to handle it even if dead to be safe as bats can carry a few dangerous diseases.
No special need for species ID, just out of interest. Both the little and southern forest bats are very common locally, although hardly seen. Just out of interest a full grown adult male weighs about as much as a 5c coin and they can live for decades. One of the smallest mammals in Australia and the world. Amazing bats.