The four-year-old was very keen from the start in first-time blinkers and after battling to hold him through the early stages, jockey Karis Teetan allowed the colt to stride on over four furlongs from home.
However, his early efforts began to tell as the field hit top gear in the straight and Stormy Antarctic was quickly swallowed up as Contentment claimed victory for John Size and Brett Prebble.
Stormy Antarctic eventually finished fifth, while the Sir Michael Stoute-trained Convey was in trouble from some way out and was last of six finishers.
Walker said: "I'm gutted, to be honest. The horse was in very good form and had the perfect preparation, so we were very hopeful going into the race.
"I'm sure people will see the blinkers and put two and two together and get five, but I think we'll be keeping the blinkers on.
"The main problem was he couldn't get any cover from his draw and he ended up in a fight with his jockey.
"He burnt up too much energy in the first half of the race and that was it."
Local star Rapper Dragon was viewed by many as the likely victor but never looked comfortable and was pulled up some way from home.
The four-year-old was taken to an equine hospital, but the Hong Kong Jockey Club later confirmed he had suffered a severe pelvic injury and had to be put down.
"It's disappointing for us, but what happened to Rapper Dragon is very sad. At least we still have a horse to fight another day," said Walker.
"I think the one thing I learned today is our horse is good enough to win these races. The fact that he managed to finish as close as he did after pulling so hard is testament to how genuine he is and how much ability he has.
"He'll have his day in the limelight, I have no doubt about that. He just hasn't been a very lucky horse since he won the Craven.
"We'll get him home and see how he is, but my feeling is Royal Ascot will probably come too soon. The only race there for him would be the Queen Anne, so you'd be going right back in at the top level again and it would be nice to get his head in front."
