This seems to be a very known story to me. So many times we had to get ready for a product demo. Believe it or not when "The moment" comes something or the other doesnt work. But yes good that LEDs were working for you. And believe me the VIPs and other big people are not always interested intechnical details.
First, it's unfortunate that you ended up in a situation where you had to dry-lab the demo, but that does happen often enough. What's interesting is the fact that the audience didn't notice.
Perhaps they were all distracted by the power-outage. Perhaps, they really didn't have much knowledge or actual interest in what they were looking at. There's a pretty big lesson on demoing here. If such folks who are paid to write about it, maybe had invested in it, don't even notice a detail like the thing is still on when all the other power is out, then how much of our presentations will they notice?
On the other hand, maybe they were just really impressed that you had managed to design in a battery back-up by launch time.