I recently posted that I lost a snake in the basement. Our "Lucky" was found without incident. Here's what I did. My first big concern was that she needed food and water. I left a bowl with water and a bowl with worms in dirt out. I put it in the utility room since that was where the most heat was generated in the basement. I placed those items on a white piece of construction paper. She would knock some dirt out if she was feeding and any water spilled would show. The only problem with this idea is that she was free to roam and not secured and safe. So here's my trap. I went to Walmart and purchased a few "Mice Cubes" These are an almost clear square plastic tubes. The front of it has a very light hinged plastic door. You place some kind of bait at the other end and set it down. The door is vented and the mouse pushes the plastic door out of the way to get to the food. Once the mouse is inside the door closes behind and the mouse is trapped. I took those traps and cut of the closed end. I then cut a square hole on the side of the cardboard box. The mouse cube is slightly tapered so as you push the cube into the hole you cut it fits very tight. Place some bait inside the box, worms, fish. etc. Punch some small holes in the box so the scent can get out. Place the traps in locations you think it would work best. The missing snake will get the scent and go looking for its meal. It will push the door on the mouse cube open, enter the box and not be able to get out. Just make sure your box is big enough that the snake must enter completely before it gets to the bait. If not it may double back and be able to escape since the door didn't close all the way. Check the traps a lot!
Disclaimer: I don't know if it really works. Looks good on paper. Lucky was found without the uses of this trap. Somebody out there prove me right and give it a try.