No, it is not. That is a common misconception.
Articles are posted from many sources and titles. The way to search is to use the operative word, in this case, "Chelsea."
If someone else has posted on the identical topic, the polite thing is to ping that post, not post a duplicate.
The one I posted is by NBC News 4:
http://www.nbc4.com/news/5499996/detail.html?rss=dc&psp=news#
The one you mentioned is Associate Press via KSFM and is not even the same article!
http://www.kfsm.com/global/story.asp?s=4223906&ClientType=Printable
Using your rationale, any two posts that used the searchword "WARONTERROR" or "BUSH" are duplicate posts. This would be insane, and you are incorrect. You could apologize, but not needed.
You are bit off in your police uniform on posting rules on this one.