One suggestion is to put either some talcum powder of cornmeal around the edges of some rooms he might be in and check it every few hours. The snake will travel along the edges of the rooms when he's on the move and when he crosses the powder, you'll see the tracks and where he's been. Also obviously check any dark closets he could have gotten into (they like to stay in dark places), cabinets and under couches, beds and also check the springs in same.... sometimes they like to coil up and stay in these areas. Don't bother calling him.... he won't hear you (lol?)
Above all, don't give up.... i've had snakes reappear more than a year after they've gotten loose.