Loss of tickets be reported to railways immediately to prevent fraudulent refunds on lost tickets.
Given in the Rules I quoted above. And I have advised you to (since you don't remember your PNR) to approach the PRS Supervisor with details of booking, date of journey, train, originating station-destination, and report loss. He will try and retrieve the data, and based on what you filled in the form as address, if you show the ID proof, he will reissue the ticket on payment of some charges.
If the ticket comes into RAC, it...
more... becomes even better. Please read the first reply I gave... BUt you said you don't know the PNR ? So approach the PRS supervisor with details.
Goodluck and good wishes.