Well, it depends on the registeration centre. Some verifiers might ask you to produce, in order to verify the registeration number.

I would advise you to tell the whole story that you lost the JEE mains admit card, the people verifying you are mostly generous and will consider your story and would allow you to proceed.

Just make sure, your Adhar and category certificate is upto date. These are the two things which they are quite pecular off!

Thank You