I don't believe that there is any way you can force a sailor to appear at a protest hearing and present a case.
As Mike pointed out, RRS 63.3(b) allows the hearing to proceed even if a party does not attend. If a competitor refuses to attend a Rule 69 hearing, the committee may conduct it anyway, but probably should pass the information to the national authority (under RRS 69.1(e)) instead.
Regards,
Eric
