I'm not sure you missed your opportunity. I did not miss my window and have been unable to get a reservation for November. However, I can get one for next week July 13. I think they just aren't released for November and later yet. It just seems too weird to me that I can get one for tomorrow (July 8) which is a crowd level 8 day but I can't get one for months down the road on a 2-3 crowd level day.
If I remember correctly, last year I got my reservation 2-3 months in advance.
When are you going? The view from this spot is the best we've ever had but if it is a lighter crowd time of year, there are plenty of good spots outside of the dessert party viewing area.
ETA: I just checked. Last year, I got my dessert party reservation 3 months in advance in August.