try creating a new category called Preview and since that wouldn't have been assigned to any pages yet, it should not appear. If you have trouble finding the article then, you could temporarily publish it either on the home page or somewhere in the menu. Then when you have found and copied the url, you can remove the article from the home page or menu or wherever you temporarily have it appear.
If you should ever want several 'preview' articles appearing on one page, create a new menu item, assign it to the Preview category you made, and in System Parameters, click on Show Title: 'No' so it doesn't appear in the menu. I don't know about what shows up in Google for example so if it's sensitive data I can't say it won't show in search engines, it probably will.
It probably appears on the Front Page because as you say it's part of the 'latest news' module. You could also try removing it from the module feed, but a new category is what I'd do.
Paul