First, lock up the cat & dog. Put towels (or door snakes :lol
under doors especially to the outside of the house, so if he is still inside the house, he cant get outside. Once you check a room thuroughly, put a towel under the door so he cant get into that room after you checked it and closed the door.
Look on and behind TV's even behind flat screens, as these are a good source of heat. If it were me I would be doing what the others have advised, then start by looking very carefully inside the enclosure (under fake grass or substrate) then look behind the enclosure, on it, in cabnet under enclosure then work your way out from the enclosure to book cases, tv cabinets, behind curtains... in or under furniture.... etc. I think you will find it is very near to the enclosure.... prolly hidden in plain sight.
My MDP got out of his enclosure and I found him in the bookshelf below his enclosure.... he didnt go far.
Do the rounds with a torch with lights out is good advice. Depending on snakes breed, whether nocternal or a climber or ground dweller are all to be a good guide as to where he might be hiding.