The correct survey number pertaining to your property can be ascertained from physical survey of the land. Any error in the survey number in your sale deed has to be ideally rectified by your seller. Since the seller is not traceable, you may request the authorities to issue patta in your name with the correct survey number. This may pose some difficulty in future transactions with respect to the property, but the same has to be managed at that point of time. It is also possible to register an Affidavit or a Declaration explaining the position. If the authorities do not co-operate in issuing the patta, you may have to file legal proceedings for necessary reliefs.