Given that this is a revival and not a brand-new show, it's possible that they could get by without the invited dress, since there have doubtlessly been other dress rehearsals. Even though the show is nearly sold-out, I would bet the producers would prefer not to cancel and refund a full house.
I am a firm believer in serendipity- all the random pieces coming together in one wonderful moment, when suddenly you see what their purpose was all along.