For every tracked keyword, BrandMentions searches everywhere and tracks the entire source to identify the mention. If you don't see the exact keyword on the page, that means that the keyword you are tracking was probably found in the:
HTML source page (Ctrl+U or right click to inspect and view the source of the page where you got mentioned, as you can see in the printscreen below, and then Ctrl+ F to find the keyword you're tracking).
in the the mention's title
in the URL