I had one hide in a stereo speaker once... turns out there was a hole in the back, and she climbed right in and took a nap. Took me four hours to find her.

If you think the snake is still in the same room, I recommend turning all the lights out this evening after it gets dark, stepping out of the room for 15 minutes (with the door closed), and then coming back in quietly and listening for 5 or 10 minutes. They're not perfectly quiet, and I've often caught my escapees rustling around in piles of paper or knocking glasses together on shelves--sometimes before I've even noticed they've escaped.

I do like the baby powder idea! Might not work if you live with a spouse/parent/roommate who doesn't want baby powder everywhere.