Jason, my sanguinity comes only after much reflection and decompressing on the issue. We talked a lot about it that night in the tent.
It really makes me think about basically every snow anchor I have ever placed and not loaded simply because no one fell.
Both the axe and the picket were buried vertically, clearly this was the critical mistake. I dug down through the powder into what I thought was firm snow, and tested it. I have decided that we need some snow school time to practice these techniques.
We are pretty experienced snow climbers and I have placed pickets as pro a number of times, though mostly in spring conditions. Everything seemed secure. It was very eye opening to put it mildly.