How to create an unlinked page

Hi,

I saw this great tactic to measure traffic from instagram, but am unsure how to create a link specific for instagram users that does not show up on my main site.

Here’s the article for what I’d like to do. Any direction on how to create such a page?
http://www.elleandcompanydesign.com/blog/2015/4/23/a-simple-solution-for-instagrams-biggest-business-dilemma