I have a 26 foot metal chimney with my furnace in the basement, and my draft has reversed twice - partly because it was warm outside both days and partly because basements tend to have a natural negative pressure. I fixed the natural negative pressure by installing vents to the outside thru my coal chute door that I open at will. I agree with Rob, 10 feet is way too short to depend on a natural draft, especially above 40 degrees outside.
I think you catch the drift on the CO detectors
they can and will save your life in the event of a draft reversal. Carbon Monoxide is undetectable by us humans. Don't depend on the faint sulfery smell to alert you of a problem, it won't wake you up if you are sleeping. Oh um, you may not wake up at all....
Another point I didn't see mentioned, everyone with a hand fired should have a manometer permanantly installed to insure that you have a draft and to see when its getting close to zero. Trying to watch smoke get pulled thru the joints in your chimney doesn't tell you how close to a draft reversal you are.
I commend your effort on spending the night at a relatives house, Good job!