It was said in the Bungie Weekly Update, open for 2 hours (Destiny)

by kapowaz, Saturday, July 26, 2014, 18:44 (3773 days ago) @ RaichuKFM

Look, I get your disappointment that you couldn't participate. That is completely understandable, and I agree that it was a dumb move to lock the moon off the way they did. It's the fact that you didn't look into it at all, which would have let you know beforehand that you couldn't do it. So my original framing was wrong, especially if you physically couldn't play the mission in the window provided. I came off really very overly harsh, and I apologise.

Fair enough.

I didn't really have an opportunity to look into it; I was attending my brother's wedding this weekend, which involved two 6 hour+ train journeys into deepest, data signal-less Wales. Also I've found the past year or so's BWUs to be so utterly devoid of real content that I've skimmed them at most (there's only so many times I can read DeeJ give some cryptic Yoda-like response to questions). So; this time I missed out on important info (not that it would have helped; I was still on a train when the availability period ended). It sucks, but I'll get over it.