You literally have to search every niche and corner of the house, vents like was said, could be in a drain pipe or any crawl place. hopefully the cat didnt find any when you were gone. I'd put the dust down to check for prints and leave miscellaneous cups of food out full that they might stick by when searching for food as youre not giving it to them each day etc... maybe leave a plant near food out, also food in open cages etc... hopefully they eat food and hide in plant next to it after.