A tipster informed us this morning that Twitter’s search engine (formerly known as Summize before it was acquired this summer) has been showing tweets in its results that don’t actually exist on Twitter itself.

These “phantom” tweets all contain the message “What a day . Wed, 08 Oct 2008″ plus a time in military format attached to the end. You can find them either by searching “What a day Oct” or simply “what a day “. There are so many of these tweets, that the term “What a day Oct” showed up as a trending tweet on the homepage for awhile.

How do we know these tweets don’t actually exist? Just click through to any of the user accounts listed and you’ll see they don’t show up in the user’s archive.

It’s not clear what is causing these inaccurate results. If the search was somehow hacked, it would raise concerns about the security of Twitter’s API. If not, and these tweets actually originated on Twitter somehow (not out of the question, especially given how fake many of the affected accounts look), then it just goes to show how easy it is to spam Twitter Search.