My MP didn't call me back, CSA says local law enforcement should deal with it, and I even called the "Saskatchewan Poachers and Polluters" hotline and the Ministry of Environment yesterday and neither of them wanted to touch this.... so I still have no idea what people are supposed to do when they find space junk.
It's going to become a LOT more common to find space junk, and I sure hope the answer isn't "just wait for SpaceX to track you down," because that seems to be the answer right now.