Bought plot without Original Documents

Hi One of our relatives was supposed to give us some money instead he gave us a plot. But he didn't had the original document and link documents related to that plot, so we applied for duplicate documents and got it registered before 5 years and now we have our original document and duplicate link documents. Now we are afraid thinking that our relative might have sold the same plot to a different party on a stamp paper and give those original link documents to them. If he had done that, will it any how effects us legally. If I give a police complaint that we had lost out original link documents, will it be helpful for us in future or is there anything to secure our plot.