142. If, where notice of the hearing has been handed or sent to the complainant in accordance with section 141, he fails, without previously advising the secretary of the section, to appear or to be represented by an attorney at the hearing, the board shall dismiss the complaint.
In such case, upon a written request of the complainant handed or addressed to the secretary within fifteen days following the mailing of the copy of the decision provided for in section 149, the board may, for sufficient cause, relieve the complainant of his default, set aside the decision and resume the hearing upon notice in accordance with section 141.