If you have a lot of coins you could try using them similar to the flour/powder idea, making a line of them along the floor and carpet.
Use a flashlight, even if you're searching during the day. They are amazing at finding the darkest little corner or area to curl up in. And the avoid open areas so check all along the walls, behind book case, dresser, etc.
Agree with Reinz that you need to look up. Like if you have a bookshelf and the books are forward so there is space behind them, it could be back there, 2nd or 3rd shelf up from the ground.
My snake got from living room into bedroom through a space where the radiator pipe went through the wall. But first I found some poop behind laundry basket, which is the only reason I knew it was in that room. Then after tearing apart the room trying to find it, it turned out to be halfway up a hockey stick I had leaning up behind an open closet door.
A patriotic Canadian snake, eh.