If just the main sail was knocked out, but the mast was in place, they should have been just fine using either a smaller sail on the main mast or a jib up front. If the mast was gone, just a small jib would have sufficed to let them limp home.
And they definitely should have had something other than a GPS, either celestial navigation knowledge or just a compass and mechanical knotmeter (tow behind type) so that they could plot their position with dead reckoning.
ectually, it's DED (as in deduced) reckoning.