The rule as in official website is:
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No refund is permissible against lost/misplaced tickets. However passenger will be allowed to travel on the reservation already made on confirmed one or RAC .If the loss of confirmed/RAC ticket is reported before the preparation of the reservation chart, duplicate ticket will be issued on the collection of the clerkage charge per passenger. If the loss of confirmed/RAC ticket is reported after the preparation of the reservation chart, duplicate ticket will be issued on the collection of the 50% of the fare . No duplicate...
more... ticket will be issued after the preparation of reservation chart in case of RAC ticket . Loss of tickets be reported to railways immediately to prevent fraudulent refunds on lost tickets.