Hello student,

Don't worry you can get it back easily by spending some days. At first you should check for it in your mail whether it is there or not as a copy. To have the original, at first you have to lodge a FIR local police station, make a copy of your marksheet or your admit card, photos with an affidavit from the court, and try to send those copies to your school principal who can help you alot in this case. If your school principal is not cooperative enough, then you should contact to your district Board from your own with all of the copies.

Hope this will help you