There are polar bears on the Hudson’s Bay coast around Churchill, Manitoba. That’s about as far south as polar bears ever get, and it’s only about a hundred miles away from this reported sighting. So, improbable as it might seem, they actually could run into polar bears — although that is a tough tough hundred miles to traverse.
I imagine that if they don’t head for the coast, the insects will get them first.
I’d guess that when it is just bush the polar bears stay farther north. Sea ice makes life easier.