I don't know what it's like at Kings Island, but all the bins lock at Cedar Point. I don't remember it always being that way though.
I think most of the rides with multiple trains now have locking bins, except Adventure Express. That was something new they did this year. If it was just my bag I would risk it but this is a camera and lenses, so I am not willing to take the risk of leaving it in a bin that doesn't lock