If the official ballots have not been received at the polling place of any town or ward on the morning of election before the opening of the polls, it shall be the duty of the town or city clerk to cause unofficial ballots to be prepared, as far as possible, in form of the official ballots. Upon receipt of such unofficial ballots from a town or city clerk accompanied by a statement under oath that the same have been so prepared and that the official ballots have not been received, the moderator shall cause the unofficial ballots so substituted to be used in lieu of the official ballots.