It's hard to know in that case. You'd hope it would be impossible to do such a thing without knowing, but in a bus it seems like it would be easier to do than in a car just because a cyclist is not in the driver's forward field of vision. The cases I find inexplicable are the ones where a motorist driving a car hits a cyclist heading in their direction. There was a case like that last year during TOSRV where the motorist came back to the scene after driving home because she thought she "hit a sign."
Some people really enjoy reading the comments to articles like that. I stopped after the first commenter turned out to be a racist.