If you still own the property, the county can seize it and sell it. If they sell it for more than the taxes owed, they get to keep the money - you get nothing. If you sold the property, the new owners are on the hook and they should go back to their attorney for not doing a proper tax search and make the attorney pay the back taxes. If there was no attorney involved, shame on them and they're still on the hook, but could sue you for misrepresentation if you led them to believe that everything was up to date.
