I won't assume the OP lost a snake, and skip over all the above perceived nastiness...
A thin line of flour going across doorways, in front of hiding places, etc can be a good indicator. As the snake travels across the flour it will leave very distinct belly tracks you might not see with salt. Aside from that what the others stated is true: tear everything apart and don't leave a single stone unturned! They can curl up into amazingly tight little snake packages and hdie in very strange places.