Look up: he climbed, then he froze
A crested gecko out of his enclosure does not scurry across the floor — he climbs the nearest vertical surface and then, as daylight comes, presses himself flat against something high and stays perfectly still. That stillness is the whole problem: a crested gecko flattened behind a picture frame or along a curtain hem is functionally invisible to a searcher scanning at eye level. Accept that the daytime search is a careful game, and plan your real effort for after dark, when he wakes, unsticks himself, and goes hunting.
Begin by closing the door of the room and removing other pets from it; a loose gecko and a curious cat are a combination that ends searches badly.
The daytime map: frames, foliage, and curtain tops
Search high and search in layers. Check behind every picture frame, mirror, and wall hanging, because the narrow shaded gap behind them is a crested gecko's favorite daytime posture. Run your eyes along the tops of curtains and the backs of curtain rods, inside the foliage of every houseplant — misted or not, plants are his natural furniture — and across the tops of wardrobes, bookcases, and door frames. Look inside lampshades and the folds of hanging clothes in open closets.
Move each item once, check it completely, and keep a mental cleared list; a gecko found and startled will jump — they are startlingly good jumpers — and a jump usually lands him on a wall or on you, so position yourself ready to cup him gently rather than grab.
Night searching with a flashlight
After lights-out, give him an hour to start moving, then sweep a flashlight slowly across walls, ceilings, and shelf edges and watch for two things: a small silhouette where none belongs, and eyeshine, which catches the beam even when the mottled body does not. Mist your houseplants in the evening; a gecko loose for a day is a thirsty gecko, and many are found licking droplets off leaves they would otherwise never leave. Set a small cup of his usual powdered gecko diet on a high shelf near the enclosure, and a second beside the plants, and note which one is visited.
The careful capture, and the tail rule
When you find him, cup him with both hands from the front and let him walk onto your hand; never pull him off a surface and never, ever take hold of his tail. A crested gecko who drops his tail loses it permanently — unlike some geckos, he does not regrow it — and a dropped tail is a lifetime change bought with one rough grab. Expect him to jump once; a second pair of hands and a waiting ventilated tub make the capture calm.
Back home, check the enclosure's doors and mesh for the gap he used, since crested geckos squeeze through feeding ledge openings and door seams keepers assume are sealed. And because balcony doors and open windows are his route out of the house entirely, tell neighbors if the search runs long: KinsLe's Lost Pet Alert System can alert nearby pet lovers for free, so if your gecko is spotted on someone's porch wall at night, the finder can message you directly rather than guessing whether he is wild.