If it is a PRS ticket and not confirmed (RAC is not taken as confirmed), approach the PRS counter immediately and you will get full refund. If it is an e ticket, it would have been cancelled automatically and the full amount will be credited to your account within 2 to 3 days. If it has reached RAC or confirmed status, file TDR immediately. Refund may take about 2 to 3 months. You will get full refund. By full refund, I mean deduction of only a minimum amount (Rs.20).