I had snakes escaped about 4 times (All my fault, I underestimated how quickly they can get out from anything). I found them all within the same day by checking around the enclosure they were in, then spread out little by little. If you have stuff laying around, gently remove them piece by piece from top to bottom. They like to hide so clutter attracts them. They also like somewhere warm. For an active colubrid like yours, I would check every room in your home. Not too fast and throwing heavy items on the floor to spook it to run from you (Which you may or may not see) and go into hiding again.
I would keep your cat away from the area you are looking. If your cat is anything like my 3 troublemakers, he or she will find it with its claws before you will.