Any such right-of-way heretofore granted which has never been used, or has ceased to be used for the purpose for which it was granted, for a period of two years, shall be deemed forfeited. The forfeiture of any such right-of-way heretofore granted, or granted under the provisions of the preceding sections, shall be rendered effective by the mailing of a notice of such forfeiture to the grantee thereof at his or her last known post office address and by stamping a copy of such certificate, or other record of the grant, in the office of the department with the word "canceled", and the date of such cancellation.