SCP-173 (lost 4chan post; 2007)
The original SCP-173 post is a 2007 4chan post that leads to the creation of the SCP Foundation.
SCP-173 was a creepypasta posted to the /x/ forum of 4chan in 2007. The post described the procedures needed to safely contain a paranormal statue that could move and attack people when not looked at. The SCP Foundation, a popular writing website and creepypasta series, originated from the post.
4chan does not save old posts, so any thread that is not externally archived will be lost. One member of the SCP Foundation Wikidot website estimated that the original post only survived for a few days before being deleted. The text and image used in the post were saved, and can currently be viewed on the SCP Foundation Wikidot website. However, many members of the SCP Foundation community and fandom have tried to find the original post or information about it. Several archives such as the Yotsuba Society, the Chanarchive, and many /x/ thread dumps stored on the Internet Archive were searched for the post without success.
Details Known About the Original Post
The oldest surviving text of SCP-173 was posted on June 22, 2007, at 12:33 PM Greenwich Mean Time (8:33 AM Eastern Standard Time). The original post was thus made on or before June 22, 2007.
The author of 173 posted under the username “The USS Walrus”. He initially planned to make a new SCP post every week, but lost internet access for a week and a half and forgot about the SCP Foundation until over a year later.  In other words, 'The USS Walrus" did not re-post the text of SCP-173. If a 2007 4chan post containing both the text of SCP-173 and the author name "The USS Walrus" is discovered, then the post will almost certainly be the original post.
SCP-173 was posted around the same time period as “Blink”, a Doctor Who episode which aired on June 9, 2007, and introduced the Weeping Angels. The Weeping Angels are sentient statutes that attack when not looked at. Members of the SCP Foundation claim that the SCP-173 post was made weeks or months before “Blink” aired. However, no physical proof exists to support these claims.  The original SCP-173 post would definitively answer whether SCP-173 pre-dated the Weeping Angels or not.
The text of SCp-173 may have changed over time. The text of the 2008 4chan post, as well as many 2007- early 2008 forum posts, varies from the current text of SCP-173. The original post will show whether the text of SCP-173 has been altered or not.
- http://www.scp-wiki.net/forum/t-228926/site-history#post-731676 Archived version
- https://www.reddit.com/r/SCP/comments/8gpt4k/does_scp173_actually_predate_the_weeping_angels/dye9zgn Archived version
- https://web.archive.org/web/20180111021822/http://z6.invisionfree.com/DeadlandsFreeRunners/ar/t68.htm, live version with NSFL images 
- http://www.scp-wiki.net/forum/t-77831/wow-i-never-expected-this#post-230929 Archived version
- https://www.reddit.com/r/SCP/comments/8gpt4k/does_scp173_actually_predate_the_weeping_angels/ Archived version.
- See: 12 (link slightly NSFW)3