Still, Kupfer, 41, took away positives from the day.
"It's one of the first times I didn't feel a whole lot of pressure," Kupfer said by phone earlier this week.
"We enjoyed it other than the 36 holes and fatigue from walking for 11 hours," Kupfer said, the "we" referring to caddie Brett Massingham. "There's not a whole lot of golfers out there who ever get a chance to do what we were doing."
Kupfer holed out in both the morning and afternoon rounds on the 394-yard, par-four 14th hole.
On the first 18, he made birdie from 70 yards and scored eagle on the second 18 from 160 yards. He shot 31 on the back nine of the second round.
"I talked to my caddie and said, 'Where has this guy been all day,'" Kupfer said.
This was the second time Kupfer played in a U.S. Open sectional qualifier. He shot 82-76 in 2009 when Saticoy Country Club hosted the event.
He hurt his wrist last year and didn't try qualifying.
Kupfer said he had a sense of the leaders' scores and where he stood after the first round at Oakmont.
"I was always around one- or two-over and never felt like I was close enough," he said. "But I am a determined person and was going to keep going even if I shot an 82. I feel like I can birdie every hole I play. The hardest thing is trying not to think about your goal score on the course."
Kupfer set out to shoot under par.
"Two- or three-under would have been acceptable, but I'm really happy with the score I shot," said Kupfer, who started two-over through three holes. "Under par would have tasted better, but it might have stung more [being closer and still not qualifying]."
Kupfer was born and raised in Anaheim, worked at Dad Miller Golf Course and started playing at age 18. He credits his grandfather for introducing him to the game.
"I love hitting balls," said Kupfer, who is self-taught and remembers the "flush feeling" from a two-iron shot 23 years ago.
Golf has taught Kupfer life lessons, too.