Ohhh...another couple of suggestions:

1. Surround the sofa with plastic grocery bags so that he can't crawl away from it without making noise that will alert you.

2. If it comes time to go to bed and still no sign of snakie....put down a layer of flour on the floor around the sofa. This will show his tracks if he comes out in the night while you're sleeping. Depending on how crazy you want to get with the flour, you may even be able to track him to a new hiding place. Messy? Yeah...but might be worth it if it keeps you from losing the little booger all together.

Good luck!!