The second place finish was enough for Ko (17, pictured right) to become the top ranked women's golfer in the world.
In doing so she became the youngest player, male or female, to reach the top ranking, breaking the record set by Tiger Woods by almost four years.
In an interview after she scrambled par on the 18th to finish alongside Jessica Korda and Ha Na Jang for second behind Korean Na Yeon Choi, Ko said the news that she had reached the top ranking eased her disappointment.
''I think it was my agent or my Mum who told me after I signed my scorecard,'' she said.
''I was like, really? I didn't know what was going to happen. I don't really know how the rankings work. Today I was just trying to focus on hitting good shots.
That's all I can do really out there. Obviously, I didn't win ... but I still got that world No 1 ranking so that's pretty awesome.''
Woods, previously the youngest golfer to reach No 1, was 21 years, 5 months, 16 days when he reached the top in 1997. Ko reached the mark 3 years, 8 months, 14 days earlier.
The men's rankings date to 1986 and the women's list is nine years old.
Ko, until recently a pupil at Pinehurst School on Auckland's North Shore, made mention of her disappointment at failing to win, but it is doubtful she would have been angry at how her round went.
Prizemoney of $US104,587 ($NZ144,248) may have also helped ease the pain.
Her swing coach David Leadbetter said his client did not really know the meaning of the word.
''We sent her to anger management school to learn how to get angry,'' he said with a laugh.
Ko, who won her first tour title as an amateur at age 15, the youngest in tour history, and turned professional at the end of 2013, has always been destined for greatness, according to her contemporaries.
''I can't say I'm surprised,'' American Stacy Lewis said of the new No 1.
''It was just a matter of time.''
Inbee Park, the former world No 1, who finished in a tie for 17th, said: ''She's probably the straightest [hitting] player out here.
''The golf gets easier if you hit the ball straight and you can roll the ball in.''
