Discontinued sign. An off-premises advertising sign shall be considered a discontinued sign where it has carried no message for a period of 180 consecutive days, or where such sign no longer identifies a bona fide business, commodity, service, entertainment or facility, or where the majority of the message on such sign has deteriorated to the condition that it is not clearly discernible. An off-premises advertising sign which has been discontinued shall be presumed to be abandoned and shall constitute an illegal off-premises advertising sign. Any period of time for which the discontinued use of an off-premises advertising sign 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 sign or user of the sign, shall not be calculated toward the number of days of discontinued use. Any discontinued off-premises advertising sign shall be removed at the expense of the owner of the sign. In the event that the owner of the sign cannot be ascertained after the Township's reasonable inquiry, the discontinued sign and structure shall be removed at the expense of the owner of the property on which the sign is erected.