Expert cave divers rescued four other people during the Thai incident, not just the 13 members from the Wild Boars soccer club.
The boys and their coach were trapped by rising waters as they explored the zigzagging passages of the Tham Luang cave in northern Thailand on June 23, reports news.com.au.
They were pulled out a week later in a three-day extraction, during which the boys were sedated and carried through the network of flooded caverns to the cave entrance.
But it has now been revealed that four employees of the Thai Well Water Association were unexpectedly found by two British divers who were helping in the rescue.
They had spent two days draining water from the cave in an attempt to try find the children. When they took a nap, the four workers found themselves trapped inside with the water rising.
The Associated Press reported that when Surapin Chaichompoo, president of the Thai Well Water Association, woke up, he thought to himself, "Why is the cave half-flooded?"
"So I ran out to look toward the entrance," he said.
"I looked back and ran to the high mound where we were sleeping. It turned out everyone had left and it was only the four of us left. I told my guys, 'Wake up, wake up.'"
He said on their third day (June 28) of being trapped, two British divers searching for the boys stumbled upon them and improvised a rescue, taking them out one by one after giving them a 30-minute crash course in diving.
The details of the little-known rescue were not released to the hordes of media that descended on the site, but news of the rescue emerged when British divers Rick Stanton and John Volanthen gave a presentation at the annual "Hidden Earth" cave community event in the British county of Somerset on Saturday.
Mr Stanton explained that the quartet had been trapped for around 24 hours and their situation was desperate, according to caving news website Darkness Below.
The two divers had only their personal equipment and there was nothing to spare for the four to use.
But they quickly devised a plan to relay the four men through the three sumps and around 700m of "open" passage back to the cave entrance.
Mr Chaichompoo said they made their way through the murky waters by swimming and sometimes walking, trying to avoid sharp obstacles in the low visibility.
Despite the risks, the two divers decided to proceed but Rick experienced a minor problem with his kit just as he submerged at the start of a sump and he had to surface again, Darkness Below reported.
However, in the end the rescue went as planned and all four men were safely returned to the surface.
"It's one of the most remarkable aspects of this whole event that such an amazing thing was a mere sideshow that never even made the press," Les Williams, chairman of the British Caving Association, was quoted as saying about the rescue of the four adults.
The incident has continued to captivate the world prompting books and film treatments in a scramble to cash in on the saga.
Adding to its interest was when tech billionaire Elon Musk took to his 22.5 million followers to call a British cave diver, who also helped with the rescue of the soccer team, a "pedo".
Vernon Unsworth has now filed a lawsuit against Mr Musk seeking more than $US75,000 ($A104,000) in damages and a court order stopping Mr Musk from making further allegations.
'THE AMOUNT OF WATER KEPT INCREASING'
Mr Chaichompoo said the group was not immediately worried because they had enough food and supplies to last a month, AP reported.
Still, there were announcements to evacuate the cave and its surroundings because water levels began to rise again.
"I was telling my guys, if it can rise it can decrease. It will probably decrease in the morning," Mr Chaichompoo said.
"But no, the amount of water kept increasing."
At one point he began to hear clanking noises under the water.
He later found out it was the sound of the British divers and their oxygen tanks knocking against the cave's walls. So he began throwing rocks into the water. After a few attempts, he finally caught their attention.
"After that I saw a flashlight begin to surface and told the guys, 'Hey, there really is someone here,'" he said.
He said when the divers found his group, they thought they found the 13 missing people.
"I told them 'No, it's four.' They said 'OK, oh my God,'" he said.
AP reported that Mr Chaichompoo said he was unable to contact the divers afterwards, but would still like to thank them.
"I really owe my life to these two divers … if they didn't save me that day, I wouldn't be here today," he said.
"If they are abroad, I will fly over to personally thank them myself."
Mr Chaichompoo said his three employees now say they will never go near a cave again.