Hmmm... I've never had to deal with that, but have heard some things on how.
First, flour lines across wherever the snake might pass could give you a good idea of his location if he leaves a trail. If this makes the floor of your place look like a chessboard concocted by a mad baker, so be it. Make sure nothing else can disturb these lines.
Second, he's going to look for a warm place.
Third, and possibly most important, snakes love snug areas where they can feel contact on all sides (like a sock drawer or something)
Fourth, snake safety. Look carefully before you sit down on anything, under cushions, etc. Also be careful opening or closing doors, cubboards, and so on. And if you have any free roaming carnivores (dogs or cats) you want to be very careful they don't find him first or mess up the flour lines.
Fifth, I've heard of people putting a dead mouse in a container that the snake can only just squeeze into. Then when the snake goes in and eats the food, he can't squeeze out again. I really don't know about that one, as it'd have to be closely monitored for snake safety, but oh, well.
Sixth, check your perimiters. If there's a chance he has escaped your house, you may want to warn your neighbors that your tiny harmless baby pet may be outside, so they'll know what it is and call you instead of taking, um... bad measures. Or even put up a lost pet/reward poster. (this partially depends on the mentality of your community)
And I don't know if this is any comfort, but I've heard of a missing cornsnake show up alive and well after something like a year. Good luck.
P.S. It's possible that www.anapsid.org might have an article about escaped critters.
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0.2 chickens
0.2 dog mutts (half ownership, only mine when they misbehave)
0.1 Halflinger horse
0.0 Arizona Mountain Kingsnake (coming soon)
1.1 parents
Still searching for 1.0 WC human