We found Sir George huddled up on the decking at the back of the house we were staying in. At first we thought he was a marsupial mouse (his body was about 5 cm long), maybe injured because he made no attempt to run away from us. Then we realised he was actually a very young baby of something much larger, maybe a possum: eyes closed, nuzzling blindly, barely able to crawl. Every now and then he'd make a chirping noise and something on the roof would chirp back. We decided to leave him alone in case his mother returned. But she didn't. The next morning we found him curled up in the BBQ cover we'd left on the ground, still chirping, still nuzzling. So we made him a little nest out of a Jatz box and tissues, hoping that his mother would come back while we were out walking. But she didn't. The next morning he was still in the box, still chirping and nuzzling, no sign of scat or mother, so we took him to the ranger. The ranger was quite pleased to receive him. "They're not common around here," he said. He then took it to a carer who would look after it until it was old enough to be set free.
Good luck Sir George.
Here's some info about Brush-tailed Phascogales