How long has he been gone for Dan. I guess its hard to judge what a sand boa will do when it gets out?
Beggining of July I have absolutly no idea where he could be. I have wooden floors in my room so ive pulled a few floorboards up and got tubs of aspen, hides and heat mat under there. Even got some live mice to try to tempt him back. Im sure he would have gone down at the first oportunity he got. When you get the sand boas out, they straight away try to bury into you.
Best of luck finding yours. I think the part about leaving FROZEN food was for the PC crowd who would be up in arms about live food being fed to the snake.