Very interesting JRiepe. From what I Googled today, the wasp closes off the opening once she has laid her egg and inserted a paralyzed larva or caterpillar for the baby wasp to feed on. The baby wasp then breaks out of the nest when large enough. Yours looks like baby was getting pretty large. Yikes, good to not be an insect.
Very interesting that this wasp lays only one egg.