I do hope you find him!
There are a couple of tricks for locating and/or trapping a lost snake which you might find helpful, if you haven't tried them already.
1) Tracking the snake - sprinkle flour or similar on the floor along the walls of the rooms in which he is suspected to be (and under any promising furniture). Snakes tend to stick to walls when out in the open. This may not help you catch him, but will at least, hopefully, give you a clue as to what room he might be in.
2) Bottle trap - there are a number of variations of this (google it), but it basically consists of cutting a 2-litre soda bottle in half, putting a brained prey item in the bottom, reversing the top, and taping it so that the snake has to sort of funnel in. The idea is that the snake eats the prey and curls up to sleep, or possibly can't leave. This can be enhanced by (1) using the prey item to leave a scent trail to where the trap will be before you tape it in, and (2) putting the whole thing under a piece of furniture, next to a heat mat or similar and a water bowl, and turning the room heat down just slightly.
Just don't be tempted to use sticky tape traps, whatever you do!
