What is the safest way to find missing snakes if they are loose in your house?
The first part of recovering a lost pet snake is a manual hunt. Get a hand mirror and a really powerful flashlight, and start looking. The most common places you'll find them is hidden behind things or wound up in the works of things like your couch. Look under and behind everything — book cases, books, shelving, walls, doors, appliances, couches, under cushions/mattresses/pillows/blankets — snakes like gaps, crevices, and dark places. Behind warm TVs and appliances are a favorite. Get down on the floor and start looking up under the stove, refrigerator, and cabinets. If you find any unfortunate holes they can crawl into (cabinets often have them up under their base), explore the interior carefully and (assuming you can eliminate the possibility of entry) close off that opening for the duration of the search.
If a quick search doesn't turn up any results, it's time to set some traps and "alarms". Snakes (both nocturnal and diurnal) like to travel at night. They also tend to travel along edges of things like furniture and baseboards. Before you retire for the night, you can lay out some thin strips of flour or corn starch at strategic places by baseboards and across doorway openings. Not only will a disturbed path of corn starch alert you to their movement, but the drag pattern will help you narrow down which room they may have entered.
You can also set out sheets of foil or that noisy cellophane wrap along their most likely routes and listen at night. Those crinkly ultra-thin grocery store bags are great. Think about all the places you checked earlier and find things that will make noise if they crawl over or under them. Nothing will wake you faster than the sound of something crawling around in your bedroom in the dark.
You can also try setting out some dark enclosures of your own. Try placing some tissue boxes, square waste baskets, boxes, bags, and blankets … anything you can snug up tightly into the corner of the wall so they have more chance of encountering it. You may get lucky.
Oh, and check the toilet, behind it and in it. It's not very likely they would go down the hole, but it's fun to wallow around in the dark cool water… if you're a snake.