Large Lizard in the Laundry

This large Blue-Tongued Lizard (about 40cm long) was in the laundry when I went to check the washing in the clothes drier. It hissed at me and I was able to open the outside door (by leaning over it) and it kindly moved outside to the mat (photographed here). It enjoyed the sun for a few minutes, before moving on. I'm not sure how many days it had been inside the house?