When I lost my blizzard, Apollo, he was gone for nearly a month. I put corn starch around all edges of the wall, and I would find that he was VERY active at nite when I was asleep.
Then, I placed crinkly paper around some good hiding places, one with a pinky under it, and I woke up one nite to hear crinkling, and found that the pinky, and snake, had dissapeared.
I put double sided tape around the walls after cleaning up the starch, and only found that once, he used the tape to shed, and another time, he just balled it up and went on his merry way.
One time I saw him crawling across my bedroom floor when I walked in in broad daylight, but he was too quick for me.
Then I made a soda bottle trap: I cut a small hole (just small enough for the snake to fit through) in the side of an empty two-liter, with the lid on, and put a fuzzy inside for him to eat, hoping that he would be too fat to escape. Usually, these traps should work! However... The next day, the fuzzy was gone, replaced by a giant blob of poop.
I ended up finding him because I left the lid to his tank open. I looked over at his tank to longingly imagine that my snake were inside, only to see him crawling back in to the tank.
It's good to do all of the things people have reccomended (I suggest the crinkly paper!) and then sit in the room in which the trap is in with a flashlite and shine it on the snake as you hear it. It should be stunned and still.
Good luck!