When it appears by affidavit that the name and residence of a necessary party are unknown to the plaintiff, proceedings against him may be had without naming him; and the court shall make an order respecting the publication of notice, but the order shall require not less than six weeks' publication.
Proceedings when name of party is unknown
Ohio Rev. Code Ann. § 2703.24, under Chapter 2703 | Service Of Summons.
Ohio Rev. Code Ann. § 2703.24