I have yet to have this problem, thankfully, but I have also seen people suggest the flour trick. Put some flour over doorjambs and along the floor. That way if you see tracks, you have an idea of what room to try the heat/hide trick with. I hope you find him!
Still nothing. This really has me upset...
I thought about letting one of my other snakes go and follow it to see if it ends up at the same spot my pinstripe is. I would assume that both being ball pythons they will both seek the same security?
In addition to the suggestion to set up a nice hidey spot, in a paper bag or sack or something; Scent it with it's preferred food item or if he eats f/t leave one in there overnight. I've heard your chances are good that it'll be in there hanging out with or digesting the food the next morning.