I know it's hard not to worry but I'm starting to relax a little these days when it happens. 9 times out of 10 I've found the snake. Once it took a whole 3 months before he showed up again but usually I've found them within the week. There are many tricks you can try, the only one that ever worked for me was putting down a heat mat with the snakes hid one it. Just a not, they will usually stay near a wall, they don't feel safe out in the open. I've found mine under laundry baskets, on top of my VCR, behind some shelving that was leaning against the wall, in between DVDs on a shelf, in between books on a shelf, in it's hide on a heat mat and once basking on my bath mat.
The next step after finding them is to fix their cage so this can never happen again. If there is any possible escape hole they will find it and use it. It's best to get a lid with a lock, you'd be amazed how much weight they can slither under to escape.