The 25-year-old Edinburgh fly-half had a chance to win a topsy-turvy autumn Test in the last moment of the game but watched in despair as his kick from 40 yards drifted just left of the posts.
Townsend admitted it was a sore one for Kinghorn, who had scored a magnificent try earlier in the match to put the Scots in front.
“For him, obviously it’s going to hurt,” said the head coach. “That’s sport. The width of a post decides whether you win or lose sometimes. He’s been kicking very well for us.
“He doesn’t kick regularly at his club, but a few number 10s don’t kick regularly. He’ll use this as a learning, so that next time he gets that chance he knows what to do technically.
“He can’t think about the fact it was a kick that didn’t go over in the last minute. It’s about what you learn from it. Do you need to keep the head down longer? Is it the follow-through? What technical thing do you need to work on?”
Another key moment in the game was Scotland substitute Glen Young’s 56th-minute yellow card – following a TMO review – for catching Tate McDermott in the head while trying to clear out a ruck situation.
At that point, the hosts were leading 15-6, Ollie Smith with their other try, and piling more pressure on their visitors, but Australia capitalised on having an extra man to turn the game in their favour.
“I was in the coaching box and (coach) Steve Tandy said, ‘Oh, we could be in trouble here’ and I said, ‘No, it’s a world-class clear-out’,” said Townsend. “It was brilliant to see someone sprinting to get with the ball-carrier.
“In his second game for Scotland, Glen was a millimetre away from the best clear-out you’ll see to hitting the smallest guy on the field in the head. I said to Glen, it was a world-class bit of play that became a yellow card.
“All our players thought they were going to the TMO because of the head shot on Duhan van der Merwe just beforehand, but that’s rugby just now. It’s the risk and reward of the game.
“Glen’s was a very good clear-out but his bicep caught the Australia player in the shoulder and chin, so that’s what deemed it a yellow card.
“It was a massive part of the game, not just because of the yellow card. We didn’t score the try from the break, but we would have had a scrum five yards from their try-line, so to go from having them under that pressure to having a penalty against us and a yellow card, it was a massive part in the game.
“We think we should have won it, but it doesn’t really matter what we think because we didn’t win. But I was proud of the how the team played and delighted with how they responded when we went behind.”
Australia head coach Dave Rennie was “relieved” to see Kinghorn’s kick drift wide as his side, with just three wins in their previous 12 matches, held on for victory thanks to a James Slipper try and 11 points from the boot of Bernard Foley.
“There was a hell of a lot of noise in the crowd, I thought it was over,” said Rennie. “There must have been a lot of Aussies or a lot of drunk Scotsmen in the stands.
“We’re happy to hang on. I’m proud of the effort, because at 15-6 we gave up a soft one straight after half-time, but we fought our way in and got our nose in front.
“We can be a lot better. But there’s been a lot of hard work from a lot of people and it was nice to get a result for the group.”