Playing in the second group out, the 47-year-old showed glimpses of the form that brought him the Claret Jug nine years ago with four birdies around the Muirfield links.
It was a rare moment in the spotlight for the unassuming Hamilton who has never won again on the U.S. or European Tours since beating Ernie Els in a playoff to claim the Open title at Troon.
"I definitely thought my golfing career would have been better after that than it was," he told reporters.
"(It has been) terrible," added Hamilton. "I try not to reflect on it. It's been trying, I guess. There's been days where I didn't want to play."
Hamilton was a prolific winner on the Japanese circuit before earning his U.S. PGA Tour card at the eighth attempt in 2003.
He won the Open and the U.S. Tour's Honda Classic in 2004 but was unable to maintain his form and has had only three top-10 finishes on his home circuit since.
"Looking back I had done a lot of good things overseas at places that people probably wouldn't know that golf even exists," Hamilton said.
"I played a lot in Japan, I played a lot in Asia. So when I won the Open I was kind of at the end. I think I was 38, so I was kind of close to the end of the decent career," he added.
"I thought it was decent, I just didn't do it on the European Tour or U.S. Tour."
Hamilton never achieved celebrity status in the United States, even in his sleepy former home town of Oquawka, Illinois.
"I think I get recognised more over here than I do in my home country which is kind of an oddity," he said.
"I walk down the street, had dinner the other night, and we were sitting outside of a little fish and chip place. The owner knew who I was."
Hamilton felt comfortable on the Muirfield links, even though he has only twice made the cut in eight British Open appearances since Troon.
"I enjoyed it," he said. "I do enjoy this style of golf. I think it takes a person that is very happy with not only their game but themselves.
"You've got to be very confident and do stuff that you feel you can do, otherwise you try to chase the game. And on courses like this it is very difficult. "
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