Discontinued billboard. A billboard shall be considered a discontinued billboard when it has carried no message for a period of 180 consecutive days, or when such billboard no longer identifies a bona fide business, commodity, service, entertainment or facility, or when the majority of the message on such billboard has deteriorated to the condition that it is not clearly discernible. A billboard which has been discontinued shall be presumed to be abandoned and shall constitute an illegal billboard. Any period of time for which the discontinued use of a billboard is proved to be caused by government actions, labor strikes, material shortages or acts of god, and without any contributing fault of the owner of the billboard or user of the billboard, shall not be calculated toward the number of days of discontinued use. Any discontinued billboard shall be removed at the expense of the owner of the billboard. In the event that the owner of the billboard cannot be ascertained after the Township's reasonable inquiry, the discontinued billboard and structure shall be removed at the expense of the owner of the property on which the billboard is erected.