Try looking in and around the nearest nooks and crannies to the Viv. The couple of times that my snakes have escaped I found them within five feet of the Viv and on one occasion that was after five days.

You could making a snake trap. Place a prey item into a tupperware tub or something similar, cut a hole in the side of the tub slightly smaller than the widest part of the prey item. Hopefully your snake will go into the tub, eat the prey item and then become trapped as it will be larger than the hole you cut. I know this method has worked for a few folk.

Good luck!