My corn snake Skittles really is a Houdini. He's still a baby, 49 grams at most, and when we first got him he was barely 10 grams :o
The first time he got out he was maybe 9 inches long, skinnier than a shoe lace, and very light, but strong. On top of that we were moving from one house to another, so I was unable to stay in the house overnight (my things were at the apartment).
I searched the first day for over an hour. I looked everywhere I thought he would be. I checked those places again. Then I searched EVERYWHERE he could be, not just what seemed likely. I searched those areas 4, 5, 6 times. I moved things around. he was gone.
I barely slept that night. I came back first thing in the morning and looked again and again. Finally I gave up. My skittles was gone I sat down on a toy box and started to cry.
And then I heard this scratching sound on the hardwood floor. I looked down--SKITTLES WAS SLITHERING RIGHT BY MY FEET!!!
That was one miracle.
I got tighter cage clips and put them on his lid. We moved him to the apartment.
Skittles is a light butter yellow color and our carpet is white. He's hard to see.
He got out another time; I found him in a box right below his cage. We put books on top of the cage in addition to the clips. He got out again, and I couldn't find him all night. I slept 2 hours at most, and on the floor in case he slithered on me. I put out f/t pinkies on the floor. I put plastic bags everywhere.
He wasn't in my room. Turns out after 6 people tearing the apartment up in search of him he was hiding out behind a bookcase...in the hall across from my room. Now I have a metal lid on his tank he can't get out of!

The point?
You have a good chance of finding them if you keep looking.
Just when I was about to give up every time he got out, he showed up.
Stay vigilant, eyes always peeled, ears too. Skittles was tiny and I still found him THREE TIMES! You'll find your ball python if you keep searching.
Look in warm places, look in low places, both of those first. Keep in mind that no place is out of reach--it might look impossible but if they put their mind to it, they CAN climb, squeeze, endure through anything! They are muscle from their head to the tip of their tail. They'll use it all if they want to!
Look everywhere, not just what seems likely. Check two times, three times, four times--and more. Keep in mind too that while you move things and walk, he'll hear you, and he'll panic and might move! So keep looking--I had checked near the toy box I found Skittles at four times before I must have moved what he was hiding under and he slithered by the box.
Eventually, they'll make a wrong move and be found.
Good luck! You'll find him. Keep looking!