I lost mine wallet with SSN few years back and went to SSN office to get it but couldn't get it 'coz they told me to bring the proof of employment. They gave me a sheet of paper that says the following numbers belong to me. But they didnt issue me the card. If you are on OPT and working legally then just go and ask for the job letter and take it the SS office and they will issue it otherwise wait  until you get a job. If you are working in college you still can get it.
p.s. You really do not need the card. Once you are issued the numbers you really don't need the card for anything. Something is already written in it anyway if you are a student, right??