I don’t remember that. How did Trump think the audience would know about it? Didn’t she say “Whew, OK,” after he accused her of going after Obama in 2008?
Notice the quick change of topic at the debate.
http://www.nytimes.com/2016/09/27/us/politics/transcript-debate.html?_r=0
This article came out a few days later and his blue curtain comment made sense.