Your question is how to know what to search for, and the answer is to search for the title of the article you want to post. FR depends on fundraisers. Bandwidth costs money, and duplicate threads eat bandwidth. So, frequent posters search to see if their article is already posted as a matter of courtesy.
See the above post 143 for an explanation of how to search if you are about to post an article. The Search function doesn’t depend on which page an article appears on, since FR gives individuals the choice of 20, 50 or 100 posts per page. It just looks for the title, to help avoid duplication.
I am not coming from the side of the poster, rather the reader, if I do not have a chance to see and read an article before it rolls off the page, as a reader, not a poster, I have no idea that it exists.
Clearly, if I am not the poster, rather the reader, I would not know the parameters to conduct a search.
I apologize if I had not made myself clear previously.