If you originally applied for your student pass through MyTSY you can also order a replacement pass through your account - sign in to replace your pass. You will be charged an administration fee (currently £7) to process your replacement application.
If you didn't use MyTSY to order your pass originally then you can also apply for a replacement card by using the paper application form (PDF) and posting it to:
Contact Centre, SYPTE, 11 Broad Street West, SHEFFIELD S1 2BQ
or drop it off at the Customer Service Desk at your local Travel South Yorkshire Interchange enclosing a cheque or postal order (made out to SYPTE) for the £7 administration fee. You can also replace a pass by phoning 01709 515151.