California Code, Labor Code - LAB § 2688

On the date and time specified in the hearing notice, the chairperson shall convene the hearing and shall determine whether each party is represented. If neither party is represented, the arbitration shall be terminated, with costs assigned to the party requesting arbitration, and the parties shall forfeit any further rights under this section relating to the dispute for which arbitration was requested. In the event only one party is in attendance, the arbitration shall proceed and the panel shall make its award based upon the evidence presented. Appearance at the hearing by a party shall be deemed to waive any alleged defect in notice.