I can tell you what I did. About eight years ago I lost my Mexican Black King snake. I thought I had pushed his bin all the way in, but I must have left it out just enough for him to squeeze through. Came home and freaked out! Spent hours searching for him. Solution? I have two dogs and two cats. The second he made a move anywhere they were barking, and hissing, and making all kinds of noise. Took me about ten minutes to locate him hiding behind the toilet. Learned a valuable lesson about how to secure my racks, and have not lost a snake since.
My advice to you (and I'm assuming you're like me and would like to prepare for every eventuality) would be to put some water in an enclosed area during the day where you can trap it easily (like a bathroom or a sparsely furnished bedroom), and then buy a really cheap motion sensor. I would do it during the day when you are at home so you don't miss it. Then when you're guy sets it off you'll be able to slam that door closed with him/her inside and then will only have a much smaller area to search. You can buy a very cheap motion sensor with a light at your local Walmart. They used to sell one with a buzzer, but I'm not sure if they still have those. I used one once to figure out which dog was getting into the trash, but mine had a camera. I picked it up off of Amazon for around $60. Was really cheap and probably wouldn't have lasted long, but it lasted long enough for me to find out it was Mohan digging into the trash every time I went to class!
And I do believe that you haven't lost your snake yet. If you are 13 and you had lost your snake I think your parents would be the ones on this site demanding to know how to find it, and then I think that would be the end of your reptile keeping days in their house. Good for you for trying to be prepared! This is one of those things it is better to have a game plan ready than for it to happen and have no idea what to do. Kind of like having a plan for when the heat goes out in winter. It's just smart to be a step ahead.
Also, for a thirteen year old you have a great amount of poise in your writing, and as a girl who graduated with a BA in English who was foolish enough to try teaching Freshman English one year I know how poorly kids older than you write. I have a great deal of respect for that, and I like how proactive you are about your herp hobbying!