My trip last weekend it only got down to 33, but I also got cold. Similar situation, mis-adjustment of gear. For me it was my underquilt. I had changed everything when I switched to the Whoopie slings, but did not check the hang of my No-Sniveler when I got in that night. About midnight, I woke up shivering & found the UQ was about 5 inches from me. BRRR! I got up, watered a nearby tree, adjusted the quilt & went back to sleep. It did take about an hour to warm back up, so I added my sit pad under me, "just because".
This was My mistake, not a gear failure. Lesson learned, I hope.