Every time one of my bps has gotten out, I have found it within 3 feet of the enclosure after ripping the room to shreds. You need to look in every single drawer and under every sock.
Also, if you put down some newspaper against some walls where it might be moving around, there is the chance of hearing it move over top of it. There are also traps you can make with a mouse inside to lure the snake in and then it can't get out. Hopefully someone else can tell you about those.
Best of luck.