His time of 22.73, on the second go, was 0.24 seconds slower than the one he posted an hour earlier.
Cooper’s first swim would have been fast enough for victory overall, with American Ryan Murphy taking out the gold medal in a time of 22.64.
Ian Thorpe was aghast in commentary for Channel Nine, claiming it was “completely unreasonable” for athletes to back up and swim again.
“They’ve got to notify the athletes. This is rubbish,” Thorpe said. “There should have been a drop [of a rope to stop athletes swimming]. There’s a huge disadvantage to those that have continued.”
World Aquatics issued an apology before the re-swim took place in what was a major blunder for the governing body.
“A technical error by an official occurred at the start of the men’s 50m backstroke final,” the statement read. “It was unanimously agreed that the competition would be re-swum. World Aquatics apologises for the error.”
Cooper did not speak to broadcasters or media immediately after the race.
Murphy said he felt sorry for Cooper.
“From my perspective it was a little disappointing how it played out,” Murphy said. “I feel for Isaac. He’s 18 years old. I talked to him real quick. I let him know in my mind, he won that race. It’s definitely a mix of emotions.”
Australian squad member Mollie O’Callaghan was quizzed about the moment before Cooper’s re-swim.
“I’m not going to lie. It’s really bad,” she said. “There’s not much you can do about it.
It has been a rough ride for Cooper in 2022.
The 18-year-old was sent home from the Australian swimming team’s training camp in Chartres in the lead-up to the Birmingham Commonwealth Games over a disciplinary breach for the misuse of prescription medication.
Cooper claimed a bronze medal in the men’s 100m backstroke final, from lane one, on Wednesday with a time of 49.52 and shaved almost two seconds off his personal best.
In better news for the Dolphins, 20-year-old Lani Pallister won the women’s 1500m freestyle by 25 seconds.
Pallister clocked a time of 15:21.34, ahead of Japan’s Miyu Namba in 15:46.76.
The 20-year-old has now snared three individual gold medals at these world titles, with blistering performances in the 800m freestyle on Wednesday as well as the 400m freestyle on Tuesday.
After overcoming an eating disorder and heart surgery, Pallister is now the first swimmer to take out shortcourse world titles in the 400m, 800m and 1500m at the same meeting.
Meanwhile, Australia claimed a silver medal in the mixed 4x50m freestyle relay.
It’s an event Australia are yet to win gold in since it was introduced in Doha in 2014. They went in as hot favourites with two world premier freestyle sprinters in Emma McKeon and Kyle Chalmers in the squad.
They were joined by young guns Matthew Temple and Meg Harris but were up against tough opposition.
France (1:27.33) broke the world record and were well ahead of the Australians in second (1:28.03).