Judging by images on Australian Lepidoptera Butterfly House and the ALA this caterpillar seems consistent with the hawk moth species: Theretra latreillii. If correct, this sighting would be right at the southern end of its known range in Australia as shown on the ALA's map of distribution of this species, see https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:2b133032-8105-4c2e-9c75-d355f1a87ba8#overview