under sec 13 of TP Act possession has given you absolute ownership of the property. u need to know that you can register now too by paying some penalty what your state requires.
when the property is in your possession more than 12 years you have adverse possession of property, the seller would be in trouble with his own sale woth the new vendee, he cannot take possession of the property as you are in possession but at the most he can file cvil suit against the seller, after all buyer beware law works.
you did not register that infirmity could be solved by deemed registration principle by the registrar under his registration laws read with TP Act sec 13 as also adverse possession principle after all yo had purchased the property which documents can be made alive by paying relevant penalties, after all your ownership is there but due to registration failure did not die but survives as far as yr right is concerned that you can move sec 17 under contracts Act 1872 ie fraud, and you can file FIR on the vendor who sold you the property as law of crimes are perpetual right given by State as State is the prosecutor.
i do not think you have lost yr property.
if desired, you send private message on my email id rapidanalysts@gmail.com
thanks and regds.