You mean, rewrite the prompt: "Please summarize the article again, but this time identify and explain any references to Geocities".
P.S. I don't mean to assume the previous commenter used ML to summarize, but it just occurred to me some people probably are, and missing details like that is probably common, more common than missing a reference the classic way, otherwise it wouldn't be a summary. At the same time, they may consider themselves to have read the article.