If (a) the mortgagee or any of his pledgees or assignees or any other person having any right, title or interest in or lien upon the mortgage shall be dead at or before the time of the filing of the petition and no legal representatives have been appointed and qualified for such person, (b) any of such persons cannot be found within this State or (c) the mortgagee, assignee, pledgee or interested person is a domestic or foreign corporation which has been dissolved or has ceased to do business in this State and no officer or agent authorized to accept service of the petition and rule can be found in this State, the court or judge, upon proof of such facts by affidavit of the petitioner, shall grant an order for the publication of the rule to show cause, such publication to be made once a week for three consecutive weeks in some newspaper published in the county in which the mortgaged property or some part thereof is situate or, if there is no newspaper in such county, by posting a copy of the petition and rule to show cause upon the courthouse door of the county for a period of three weeks. Such constructive service shall be complete upon the expiration of twenty-one days from the time of the first publication or posting of the petition and rule to show cause.