The 24-year-old became the first swimmer to reach the 200 meter butterfly final last weekend, despite the fact that five family members were not found and his parental home in Kerala was destroyed by high water.
Prakash finished fifth outside the medals, but his prayers were answered after an uncle called to let him know that his relatives had survived the devastating floods in the South Indian state and had killed more than 350 people.
"I had trouble sleeping, thinking of my family," said Prakash. "I had not heard from them because they were cut off from the (telephone) network and unable to contact us," he added.
"I was very nervous but my uncle called to say that they are all safe and all is well at home."
Prakash's mother Shantymol, who is based in the neighboring state of Tamil Nadu, initially kept the news about her son's disaster so that he could concentrate on his achievements.
But after he had heard from friends about the floods, Prakash had to put his worries aside, despite the fact that he had lost contact with his relatives, without receiving notice from Kerala for three days.
"I knew the rain was starting to get worse (in Kerala) when I arrived in Jakarta, but I did not know it was that bad," said Prakash after the 100 m flying flags.
"But that's what we train for – to swim under pressure, if I think about it, I'll spoil it here, and if I ruin here, they're both sewn in. Anyway, I can not help it, I have to just concentrate on what I have to do. "
After he was the first Indian swimmer to reach a final of the Asian Games in over 30 years, Prakash scored a national record of 57.75 seconds in one minute – a distance of 3.22 seconds behind the Japanese winner Daiya Seto.
Prakash, who swam to India during the 2016 Olympic Games, insisted that he had never thought of leaving the Asian Games.
"I have been preparing for this for a long time and I did not want to ruin it by going away," he said. "My teammates kept me busy and focused – being with them is something other than being alone."
"It was my dream to win a medal at the Asian Games from childhood," Prakash added. "I worked very hard for it – I did what was possible to do, and if I had placed the top three, it would have been a gift for my family.