Any person claiming damages as compensation for or on account of the construction of the improvement shall file a claim in the office of the county clerk at least three (3) days prior to the day on which the petition has been set for hearing, and on failure to file the claim at the time specified shall be held to have waived any rights to the claim; provided, that if the person is an infant or adjudicated incompetent and without regular guardian or conservator, or the guardian or conservator has not been notified of the proceedings as provided in §§54-12-128 —54-12-131 for notice, and the facts are made to appear by affidavit, the monthly county court shall appoint a guardian or conservator ad litem for the person, who may file the claim for damages, if deemed proper, for the person under disability, within the time allowed in this section or within three (3) days after the appointment.