The only two snakes I lost were found in a moving box with a bunch of stuff in it, and behind some cardboard that was leaning against a wall.
The snake is in the one place you haven't checked. Wherever you think they couldn't have gone, they are there. I've heard of snakes being found in laundy, in subwoofers. Basically get on the ground and pretend to be the snake. they like to travel along walls and are just looking for a secure place to hold up. Generally they don't move a whole lot once they find a good spot. I've found all my snakes within hours of escape.