Yes you can get PNR details from PRS. you have to mention them train number, name, your name as mentioned while booking, journey date and boarding point. they will have access to list of people booked under one train. But you need to give them a written request with FIR(i guess) as ticket lost case

i had already written in blog, Re# 446116-2 "i don't know whether you can get duplicate wait listed ticket or not ,but you can know the PNR number.For that you need to remember your date of journey,your train number,boarding station and "reservation from" station and the booking status W/L number.you give all these details to PRS they will tell you your PNR. (Booking status: suppose for e.g a ticket is W/L 110 / W/L 45 the left side i.e W/L 110 is booking status.It won't change with time)".
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getting PNR details is not much issue.But the issue is duplicate ticket for a waitlisted one.Do the railways allow duplicate tickets for wait listed tickets?

Yes there is always a clause for issue of duplicate ticket in lost/stolen case. And that is not restricted to Waitlist/RAC.

Nahi Shrimaan, waiting list tickets ko kabhi duplicate ticket nahi issue kiya jata hai. Ya to apko rac ya confirm hone ka wait karna hoga, ya phir paisa doob gaya agar apka ticket wiaitng me hi reh jae chart ban ne ke baad bhi.

I partly agree to Bhopal shatabdi,but as per my info railways only issue duplicates for CNF tickets not even for RAC . Have you heard/read/seen any such for RAC?perhaps not

Rac ko bhi diya jata hai sir, kyonki unhe bhi train par chadhne ka adhikaar hai.

logically i agree you.But once i had lost my ticket at NDLS which was RAC,chart prepared. I reported to police. i went to railway officials and asked, also went to ticket counter with documents.But he told me that ,had been it would have confirmed you would have been issued a duplicate tickets after paying some charges(i donot rember that now).But as this is RAC you won't be issued duplicate.This was year 2010 summer.may/june/july/aug donot remember that.

To phir main galat ho sakta hu. Aapne khud aajamaya hai, maine to sirf idhar udhar se suna ya padha hai. Bura mat maniyega, main apki baat se inkaar nahi kar raha, par Ye bhi to ho sakta hai ki niyam badal gae ho, ya uss karmchari ko pata na ho, ya phir wo thoda paisa khichne ke chakkar mein ho aur aap samajh nahi pae.

may be you are right.rules may have changed from 2010 to 2012(now).That's why i wrote the time i.e it was 2010.