SER won't verify a link if its not shown in the html source of a site. i think in your case it was just bad timing and your site just died (traffic limit exceeded for example) between when SER verified that link and you discovered the 404.
the verification link should be deleted when you re-verify the site which you should do anyway frequently if you haven't the re-verify option checked already in your project options.
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But it clearly returns 404 response in header.
also i accidentaly clicked accept