Procedure to get copy of missing sale deed of property

After the recent death of my parents and while selling of our Shop (which is closed now), I (being only child) found that Original Conveyance (Sale) Deed (standing in my mother's name) of said Shop is missing and there is no Photocopy / any kind of Details of said Deed. I only know following: 1) Names of Seller & Buyer 2) Date of Registration (here xx.xx.1992) at Alipore ADSR – Kolkata. 3) Only Page Nos. (here X to XX) - (do not know Book No. & Vol. No.) 4) Address & Location of Shop (here under Patuli PS) . Further, I made concerned online Search (by putting First Name of Buyer and Registration Year 1992 and District of Registration) - but all Search Results show from Year 1993. In this regard, please advise to where should I contact (in person) in order to get Deed No.; Book No. and Vol. No. - so that I can put a Missing Diary and obtain Certified Copy (after due processing). Can I get the Details through RTI..? If so – mention procedure.