Clematises can recover despite what humans and nature can do to them. Try scratching the bark and see if it's green (good news) or not.
I doubt if you killed it. You can prune it as a group/class 2 or 3. I'm uncertain why you left the 5' woody stem. If it was in my garden I'd cut it back to the ground and give it a big drink of Epsom Salt - one tablespoon to a gallon of lukewarm water. It will encourage more stems to sprout. Please add mulch to keep the soil evenly moist.
I've never gardened in your area so contacting your local Cooperative Extension Service could be helpful if they're familiar with the plant.
Here's more about it here:
http://www.missouribotanicalga...
Let us know what you do. Good luck.
