As everyone else has said - don't give up! Keep searching - in crevices, dark spaces, warm spots. A few years ago one of our Corns - then a baby - escaped and was missing for 5 days. He turned up in the same room hiding in a bag! Another of our Houdinis managed to push his way out of his tank one night and was found right next to it curled around the computer where it was warm

When I was 11 and had my first corn snake, my then baby brother managed to take a heap of stacked books off the lid of the snake's cage - used to secure the lid from escaping serpents!! Again the snake was found in the same room - curled up with some wires behind the tv, perhaps he thought they were fellow snakes

(Needless to say, since these experiences, all of our snakes have locked or stopped cage doors!!)
A couple of tricks include; putting out some hides, half over a heat pad. Leave some water there in case he turns up and is dehydrated, and you can also try leaving a food item out - if he is hungry the smell might lure him. Try putting the food item in a bottle, cut in half, with the end over a heat pad, in a dark area - this might hopefully bring the snake out and then after eating he will be tempted to lie in the warm, dark spot to digest his food! Anything is worth a try!
You didn't mention what kind of snake it is or how big?
DO NOT use duct tape - this is highly dangerous... if the snake gets stuck or caught on the tape it could end up severely injured from the struggle of getting away from the tape, or worse it could end in death. Use only humane ways of tempting and catching him, and hopefully he will turn up. Good luck, i hope you find him.