found this on the KingSnake page - maybe you've seen it already... Sounds like you might want to look behind your oven/stove - My friend's wife was scared out of her mind when their missing snake dropped down from the oven hood while she was cooking - YIKES! Good luck finding Fred!
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ESCAPE! One of the worst feelings I've had is the realization that the snake in not in it's cage. Most often it's due to the fact that you've forgot to secure the cage. If this unfortunate event happens to you, there are a few things you can do to get it back. First off, try and pinpoint exactly when it got out. If it's been a few hours, it's most likely in the nearest spot which is small, dark, and warm (like the cushions of a sofa). If it has been awhile, you Ball Python may be anywhere in the house. Good placed to look are around or in appliances that give off heat: Refrigerator, Oven, Water Heater, TV, VCR, etc. It's advisable to look at night, since Ball Pythons are nocturnal. You may also want to set a scent trap, which may or may not work. Drag a prekilled rodent (a gerbil would be best) along the base boards of the room(s) that you think your snake might be in. Then place the rodent into a cardboard box that you've cut an access hole into, and place the box in a corner. You may want to put a heat pad under the box. The reasoning is that chances are the snake will crawl along the wall, hopefully pick up the scent trail and follow it into the box. Once in the box, it may eat and decide to stay in the dark warm location and digest. You may also want to restrict other house pets like cats and dogs, from being in the room(s).