Petitioner must file a declaration describing efforts made to locate a person entitled to notice in a proceeding under the Probate Code, but whose address is unknown, before the court will prescribe an alternate form of notice or dispense with notice under (c). The declaration must state the name of the person whose address is unknown, the last known address of the person, the approximate date when the person was last known to reside there, the efforts made to locate the person, and any facts that explain why the person's address cannot be obtained. The declaration must include a description of the attempts to learn of the person's business and residence addresses by:
Mailing notice to a person at a county seat is not a manner of giving notice reasonably calculated to give actual notice.
If a person entitled to notice cannot be located after diligent search, the court may prescribe the manner of giving notice to that person or may dispense with notice to that person.
Cal. R. Ct. 7.52