is take a deep breath and take a moment to calm down. I know first hand that racing around trying in a frendzy to find something is just going to get you upset and unable to find what your looking for.
If you have honestly checked everywhere you can think of, then here is what i've read people suggest. set up a light, red is preferable, and a water dish. Under the light put his/her favourite hide.
Your gecko is there, hiding, and i've also read of geckos missing for months and then being found. If your sure there is no route of escape then block off any space under your door, if there is one and just wait. You can try to look again in a while but do it slowly and take a flashlight and look under and behind all furniture.
You'll find him i'm sure....
Red 
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Crested Gecko Zeek:1.0, Ziggy and Zeus
LEOS: Boo: 1.0 normal , Bronx & Nala: 1.1 blizzard,
Lily: 0.1 patternless, Abby: 0.1 albino, Zoe: 0.1 reduced pattern, Dot: 0.1 hypo
New Girls: Flame, Karma, Bubbles and Bell pics coming soon
Chip: 1.0 papillion (small dog)