Even during the Summer, I carry an Adventure Medical SOL Emergency bivvy sack, as well as fleece jacket, Gore-Tex, rain gear, extra energy food. During the Fall and Winter I carry a one pound Gore-Tex bivvy sack on day hikes. Either of those two items, or something similar, would have helped you spend a more comfortable night.
For overnighter's I'm never without the Gore-Tex bivvy sack or one-person tent, to supplement my sleeping bag, regardless of a nice weather forecast.
My philosophy is to be prepared to spend the night safely, and survive, especially if injured.
