So if you search Person A and get an article that apparently never says “Person A,” several things could explain it:

- Other pages may link to that article while discussing Person A. Google explicitly says the words used around links to a page can help determine that page's relevance to a query. blog.google

- The article may be semantically connected to Person A through people, organizations, events, locations, or topics that Google's systems associate with them.

- The name could exist somewhere Google indexed that you don't immediately see: metadata, an earlier version of the page, captions, structured data, embedded material, or text omitted from the search snippet.

- The broader web may strongly connect the person with the event. If hundreds of pages, forums, social posts, etc. discuss Person A → Event B → Article C, Google can potentially recover Article C from the concept represented by Person A even if C itself doesn't contain the name.

- Search behavior can help Google understand query intent at the aggregate level. Google gives examples where its systems have learned that people issuing a certain ambiguous query usually want one interpretation rather than another. blog.google

- Some results can also vary based on context such as location and personalization. blog.google

The interesting case you're describing is therefore quite plausible:

Person X

→ lots of people/websites associate X with Incident Y

→ Incident Y is strongly associated with Article Z

→ Google retrieves Article Z for Person X

even though:

"Person X" ∉ Article Z

Google effectively has a large latent relationship graph between queries, entities, concepts, links and documents rather than a simple keyword inverted index.

I wouldn't infer from the result alone that Google has evidence the rumor is true. Search relevance means Google's systems have inferred that the document is relevant to what people seeking information about that person might want. Those are very different claims. Google itself cautions that its systems use signals to assess relevance and quality and don't understand truth in the human sense. blog.google

One potentially revealing experiment is to search the person's name in quotation marks. Google says a quoted search generally restricts results to documents containing that exact phrase. If the strange article disappears with "Firstname Lastname", that is good evidence the unquoted result was being produced through Google's semantic/association machinery rather than a literal occurrence of the name.

(http://www.autoadmit.com/thread.php?thread_id=5907922&forum_id=2#50162066)