Diamonds are the only python native to the area (for several hundred kilometres). In my opinion that is certainly not a Diamond hatchling, given the size and shape of what should be “rosettes”. Here is a photo of a couple of typical Diamond hatchlings, plus a pic of the parents, so you can compare…
http://www.aussiepythons.com/forum/sale-snakes-43/diamond-python-hatchlings-157926/#post1914503. It does however have the markings you would expect for a straight coastal hatchling. Diamond x Coastal offspring can have similar markings.
I would say it is either a straight Costal or a Diamond-Coastal cross hatchling.
To be a straight Coastal it would have to be an escapee from someone living quite close by as it would have had to make its own way your house. To be cross would require that an escaped adult Coastal mated with a local adult Diamond. Given adults’ capacity to travel distances versus that of a hatchling, I would say the latter is the more likely scenario.
Blue
PS I don’t see why the “hybrid” (sic) scenario is jumping to conclusions in this particular case.