ORS 105.230: Service by publication.

If a party having a share or interest in or lien upon the property is unknown or cannot be found, and such fact is made to appear by affidavit, the summons may be served on the unknown or unlocated party by publication, directed by the court or judge, as in ordinary cases. When service of the summons is made by publication it must be accompanied by a brief description of the property which is the subject of the suit.