As said somewhere else (currently immediately above, but that could change!) possibly the other was sbmitted at a different time of day.

Also, the other URL has additional parameters - RSS feed, something else - so the URLs don't match exactly.

The other attracted no comments, maybe this one is better timed. It's one thing I wish could be fixed on HN. It's one thing for submissions to be ignored, but having them not seen at all seems a bit of a waste.