Pubcon #1 for robots.txt in Google

I was shown a very unusual result in the Google SERPs today. Take a look at what the number one site is in Google for the query "robots.txt":

Pubcon.com does not mention the word robots.txt anywhere in the document and looks like a highly unnatural result for the query.

Here is a screenshot of the Pubcon.com homepage with nothing about robots.txt on the page:

What was the previous #1 result for robots.txt? Was the old #1 result in Google redirected to Pubcon?

It is interesting that Pubcon.com is the #1 result for robots.txt, because Webmaster World is also associated with a famous PageRank 6 robots.txt file.

WebmasterWorld.com is also famous for search engine cloaking, and clogging up the Google SERPs for tech-related queries with login screens.

Does anyone know the answer to the puzzle of how Pubcon got the #1 spot in Google for robots.txt? What was the original #1 result for robots.txt, and is there a 301 redirect involved?