My dad, born and raised in Northern Ontario, knew how to, and had built birch-bark canoes.
Well, sort of like the wadding discussion, I don't think you can say that very short barreled long guns "did not exist". "Coach guns" did exist, and really there's no difference between the two. Perhaps the term "canoe gun" did not exist. I just don't think anyone cut a long barrel down for the express purpose of being "more handy" in a canoe. A "canoe gun" would probably be more desirable as a "cabin gun", or a "teepee gun". Perhaps more friendly to carry when running a trap line. ??
I don't doubt that they "existed", but I'm quite sure that a long barrel musket was preferred 99% of the time, at that time period.
Again, I'd love to have one for berry picking, trekking, hiking, exploring, but would not choose it over my Jeager or Brown Bess for actually hunting.