Dear student,

If you have lost your Admit Card, then you should report to your department teachers. They will provide you a duplicate admit card. And also sometimes, they will ask you to file an FIR for lost property like certificates etc. Because some other person who founds your old admit card might use it in wrong way. So, you also have to file a FIR. The whole procedure will be tell by your respective department teachers. So contact them.

Hope it helps.