Well that is frightening.
It's time to think like a snake! I like warm dark places where I can curl up and not be disturbed. Think about how I would get out of my enclosure. The path I would take once I had escaped. I try to get down to the floor. I'll slither across desks and shelves and into piles of laundry. I'm usually pretty close to where I normally live, but I can travel into other rooms if the door is open! I'm going to get nice and comfy here wherever I am..You'll find me eventually!
Check everywhere. And then check everywhere another 3-4 times. Then check again. Make sure you are looking at any possible place the snake can hide.