Make the search safe before it starts
An escaped snake is frightened, not aggressive, but a safe search is still a planned one. Shut other pets and children out of the search area entirely, both for their sake and because a wandering cat will find the snake before you do and start a fight nobody wins. Wear shoes, carry a torch, and have a snake hook, tongs or at least a long broom handle to hand for moving cushions and clutter, because the rule of the whole night is that you look before you reach. One firm exception: if the escaped snake is a venomous species, or a large constrictor beyond your experience, do not search by hand at all. Keep the room closed and call a professional snake catcher or your local rescue for help.
Search low, slow and along the edges
Snakes travel by hugging structure, so your search pattern is the perimeter, not the middle of the room. Start in the room the vivarium stands in and work each wall in turn, torch beam low and angled so it rakes along the skirting board. Then work the warm machinery: behind the fridge, around the washing machine and dishwasher, the boiler cupboard, the backs of radiators, anywhere a motor gives off steady heat. Check inside the sofa base, under loose cushions, in laundry piles, shoe rows, and the warm tangle behind entertainment units. Move everything slowly and put it back as you go, because a snake disturbed too roughly bolts to a deeper hiding place and the search starts again.
Let the room report back to you
You cannot watch every wall all night, so recruit the room itself. Lay crinkled plastic bags flat along the skirting boards of the likely rooms; a snake crossing one in the small hours makes a sound that carries through a quiet house and tells you which room to concentrate on. A light line of flour dusted across a doorway threshold does the recording job silently, showing a smeared crossing by morning. A shallow bowl of water placed against a wall is worth adding too, because an escapee that will not show itself will still come out to drink.
Warmth, patience and the second night
Most escaped snakes are found within a room or two of the vivarium, curled in the first tight, warm, dark space that felt safe. If the first pass fails, set a warm hide, a box with a heat source safely outside it and a familiar-smelling item of enclosure furniture inside, against the wall of the most likely room, and re-check your listening bags and flour lines as the night settles. Repeat the edge search quietly the following night before widening it; snakes are patient, and a methodical second search usually beats a panicked first one.
If the signs point outward — an ajar door, a flour trail heading the wrong way — act quickly through the Lost Pet Alert System in KinsLe: it sits free inside each profile, places a marker on a map, and lets whoever finds the snake message you without an intermediary.