It was your fault to purchase a property without getting a legal opinion. Mere newspaper publication cannot satisfy the purchase norms.The link document of previous buyer shall not be sufficient to buy the property. All the link documents right from mother deed should have been verified and scrutinised before purchase, that is why people flock to advocates for getting legal opinion before purchase. This small fee to the advocates for the purpose of legal opinion will save lakhs of rupees getting blocked by was of legal hassles and complications at a later stage, a situation similar to yours. The claim for adverse possession an perfecting the title can be made only by the person who is holding the property by that situation whereas you have a registered sale deed so you are not entitled to claim to perfect he title by adverse possession neither your vendor. The original vendor who sold this property to your vendor should have perfected the title by adverse possession by obtaining at least pattadhar for the property from the revenue department to prove his title. Mere occupying the property for years will not entitle a title to him on any basis, he ha to apply for it before the government authorities, who will sanction a patta on his name to confirm title on his his name after which he will acquire marketable title by which he is entitled to sell the property to a third party. If the government property has been illegally sold or purchased, then the entire transaction i invalid, therefore you may pressurise the vendor to return the consideration amount or else you may lodge a criminal complaint against him for cheating, let him explain or fight against his vendor.
Alternately you may file a title declaration suit, no doubt the same may not stand ground for the case to disposed in your favor, but by impleading the vendor as a respondent, you may have an alternate prayer seeking court direction to instruct the respondent/vendor to return the sale consideration amount obtained by him in case the court decides that you cannot get the title of the property declared on your name.