The usual procedure is as follows:
1. File an FIR at police station and proceed to Railway Station
2. Ask for Station Superintendent and furnish details of journey date, train no., booking date, PNR, proof of passenger name and age.
3. Upon payment of 25% of fare and undertaking letter, the Station Superintendent will get the reservation counter to issue a duplicate ticket
Duplicate...
more...

tickets may only be issued in case of torn/ mutilated confirmed or RAC tickets/ lost as follows:
A. Before Preparation of Chart:
Conditions Distance Payable Fare
Torn / Mutilated Confirmed / RAC
Tickets for all trains except for
Shatabdi / Rajdhani 1st 500Kms 25% of total fare
Above 500kms 10% of total fare subject to a
minimum of 25% of total fare
For Shatabdi / Rajdhani Trains All distance 25% of total fare
B. After Preparation of Chart:
Conditions Distance Payable Fare
Confirmed mutilated /
Torn tickets 1st 500kms 25% of total fare
Above 500Kms 10% of total fare subject to a minimum of
25% of total fare
Confirmed lost tickets All distances 50% of total fare
RAC / Mutilated / Torn
Tickets All distances 25% of total fare
Duplicate Ticket Refunds:
Cases where lost tickets are found and presented together with duplicate tickets before train departure, a refund is permitted subject to 5% deductions for charges subject to a minimum of Rs. 20/-. Only then is the original ticket valid for travel.
Krishanan Manthal

If the reservation status of the lost, misplaced, torn or mutilated ticket is reserved or RAC and duplicate ticket is sought before preparation of reservation chart, the station master shall issue a duplicate ticket in lieu of the original ticket on collection of the clerkage charge per passenger.
(ii) If duplicate ticket in lieu of a lost or misplaced reserved ticket is sought after preparation of reservation chart, it shall be issued on collection of 50% of total fare. Duplicate tickets shall not be issued for RAC tickets after preparation of reservation chart.
(iii)...
more...

If duplicate ticket in lieu of a torn or mutilated reserved or RAC ticket is sought after preparation of reservation chart, it shall be issued on collection of 25% of the total fare.
2) (i) No refund shall be granted in respect of charges collected for issuing duplicate tickets except where the lost or misplaced ticket is traced after the issuance of a duplicate ticket and presented alongwith the duplicate ticket before departure of the train. The charges collected for issuing duplicate ticket shall be refunded after deducting five per cent. thereof subject to a minimum deduction of rupees twenty. In case the journey is also not undertaken, the cancellation charges on the original ticket shall be determined as provided under Refund rules.
(ii) The passenger, who has paid excess charges in train on account of his reserved ticket or RAC ticket being lost, misplaced, torn or mutilated, can make an application to Chief Commercial Manager (Refunds) of that Railway administration for grant of refund of the charges paid in train, who may, if decided, grant refund of the charges realised in the train after retaining the cancellation charges at 50% of fare per passenger provided that no one has taken refund earlier on the original ticket.