How to cite information removed from a working paper when it was published
This is a rare situation, because “interesting enough to cite” and “interesting enough to include in the final draft” tend to be highly correlated. Therefore I wouldn’t expect there to be a “standard” way to do this.

However, there are standard ways to cite working papers. For Chicago style, it’s this:


  Author. Year. “Title of Paper.” Title of Series. Sponsoring Organization, Month Day. 
  
  Add URL at the end if available online.
  
  Deal, Ashley. 2009. “Collaboration Tools.” Teaching with Technology Whitepaper. Eberly Center for Teaching Excellence and Educational Innovation, Carnegie Mellon University, January 23. http://www.cmu.edu/teaching/technology/whitepapers/CollaborationTools_Jan09.pdf. 


Source: CMOS 14.228, as quoted here.

I would switch the first part of your citation to match this format. The additional commentary that the result was excluded from the final paper is, in my mind, extremely important to include. I would do exactly what you’ve done (after correcting the second citation to Chicago style as well).