On meta, I searched for a way to show the notification messages again how can I view the SO notifications again
There were no helpful answers, so I went to the Ask question button.
After putting my search sting into the title of my "new" question, my very question (and answer) showed up in the suggestions. So, the word again was the showstopper.
After this experience, I guess that the search function uses each word to restrict the results whereas the suggestions have a more sophisticated algorithm to show "similar" questions. But I wanted to be sure about this. If the help page on searching contained also "unrefine" hints, I'd not have asked this question.