Are you sure about that? The star over each icon indicates that both of them are bookmarked.

So either this is a bug or there is a second bookmark hiding somewhere. If you go to Bookmarks > Manage Bookmarks and search for “qb”, what appears there?

To delete old suggestions based on previously visited urls you should be able to press the down arrow to select it and then shift + backspace to delete its memory of that suggestion. Sometimes I have to do it multiple times if multiple similar urls that don’t exist anymore are still being suggested.

This is assuming the incorrect one isn’t also bookmarked or being suggested for some other reason besides being visited in the past.