In my opinion, in an emergency overnight ordeal, you will not sleep, either because you will be too stressed out or you just won't feel like sleeping at all...

A basic silnylon tarp will allow you to protect yourself from the wind and rain, you already got a Heatsheet so that's good, and you also need some form of insulation from the ground. A foam bum pad is the minimum, you could get one that's torso-length for more body coverage.

Just build a fire, gather some firewood, sit down and let the night pass... if you've never experienced such a thing, you will realize that the night goes by pretty quickly when you are busy gathering wood (a good folding saw is a MUST), thinking of a better way to keep your fire going, sipping on water here and there, looking through your survival stuff... trust me!

I've spent a few nights in the wilderness without sleeping at all, in the winter (< 5 &#8457; temperature), simply by building a big fire and pitching a tarp properly.

P.S. : Dry socks are a very, very nice touch, always carry a spare pair in your backpack, even for short hikes.