close all access to the out side, then put a small pinkie in each room at night (to locate the animall) and check under anything that gives off heat, like the washing machine, airing cupboard and the dishwasher. Also cover up any air vent sand other places it could squeeze though.
If you want to see a snake constriced f/t food, then feed it on forceps or with gloves (or even by hand if youve got the balls)