It makes me sick to the stomach, but I'm actually not shocked that Halep lost to Kanepi. Kanepi's game is a lot like Lucic, who is 2-0 v. Halep in slams, and the one time they played previously, Halep won in a third-set tiebreaker.
Halep was flat today, which is understandable given she already accomplished her career goal of winning Roland Garros and had played her butt off in the two summer tournaments before the U.S. Open.
It's incredibly disappointing she did not find a way to win after erasing an 0-3, two-break deficit in the second set to make it 4-4, 40-15, but if Kanepi keeps playing like that, she can beat anyone. She hit the ball flat, deep and within a foot from the baseline from start to finish and only had the one bad patch of missing/choking along the way. Halep always will be vulnerable to players like that.