If a party designated to be served in § 16.1-263 is without the Commonwealth but can be found or his address is known, or can with reasonable diligence be ascertained, service of summons may be made either by delivering a copy thereof to him personally or by mailing a copy thereof to him by certified mail return receipt requested.
If after reasonable effort a party other than the person who is the subject of the petition cannot be found or his post-office address cannot be ascertained, whether he is within or without the Commonwealth, the court may order service of the summons upon him by publication in accordance with the provisions of §§ 8.01-316 and 8.01-317.
Va. Code § 16.1-264