Yes. First you need to keep your calm. Do not panic. Contact your school immediately. They should usually keep a copy. If not, they will contact the board office.
And look well around your house, like Mony said. You are sure to find it in some place.
Yes, always make a photocopy henceforth.
Now, if you don't have an entry, it is upon the school and the board whether they'll let you sit for it or not. I will hope things go right for you.
Next time, be careful
Take care