The search term quick attack reports on the performance of search terms, not necessarily what is already a negative keyword or not. For example, you might add it to one place as a negative, and then later decide to remove it as a negative. It will still appear in your search term report.
But the good news is - we are improving this tool's functionality by adding a 'previous action' button, which will show you what actions you have previously taken on this search term. We expect that to be done in the next few months. We think this will help boost efficiency in a big way and can't wait to share it with you!