(a) If, at the time of or subsequent to the filing of the petition, the petitioner shows by affidavit or otherwise that the petitioner cannot after due diligence ascertain the name or location of a person that the petitioner is required to, or chooses to, serve under G.S. 46A-21(b), the court shall authorize service by publication under G.S. 1A-1, Rule 4. The notice by publication shall include a description of the property that includes the street address, if any, or other common designation for the property, if any, and may include the legal description of the property.
(b) Before or after the notice by publication, the court shall appoint a guardian ad litem under G.S. 1A-1, Rule 17, to represent any unknown or unlocatable person that the petitioner is required to, or chooses to, serve under G.S. 46A-21(b).