Lost sale deed and fathers Will document

My mother passed away in 2009 and father remarried in 2012. My father passed away in 2014. He made a Will to distribute the property for me and my sister in 2012 before his second marriage. For safe custody we had kept the original sale deed and the Will document with one of our relative. Unfortunately both the sale deed and the Will document went missing from there. We have taken a duplicate copy of the Will document from the Sub registrar office. Following are some of my doubts: 1. What are the possible ways that someone who got the original sale deed and the Will document misuse it? 2. Is it possible for a person who has access to the original sale deed and the Will document to submit them to any bank or other personal to get loan without our permission? 3. What is the possible way to check for the current liabilities on our land? 4. What are the next procedure to be followed to get a sale deed and register the property in my name and my sisters name? 5. Read somewhere that we would need to file an FIR for the lost sale deed. Do I need to file it to the police station on the location of property or the location from where the documents went missing? Thanks