This answer was posted at
2014-07-30 04:24:50Z, which is almost three hours after the question was closed at
This is the second time I've seen this. The first time a comment exchange followed along the lines of "how did you do that?" A: "bad site scripting I guess".
It seems like this happens when an answer is started when the question is opened, left for a while, and then submitted after it's closed. However it's happening, it's a significant bug that impairs the proper functioning of the site.