Ms Tropea, of Towradgi, was driving home from Sydney when she got stuck in traffic after a car crash at Bulli Tops.

Her son, Cruz, soon became ill in the searing heat. It was over 30 degrees in Wollongong, and much hotter on the baking roadway in a rapidly heating car.

"Before I knew it, he got really bad. He was so dehydrated. His eyes were in the back of his head, he couldn't even walk," Ms Tropea said.

"A couple came over to give us some water to wash him down, but he wasn't getting better."

A truck driver offered to let Cruz lie down in his cool cabin, giving him cold water and fruit. Cruz recovered slightly, and the driver helped them back to their car as the accident cleared.

In the confusion and concern over her boy, Ms Tropea never got a chance to ask the truck driver's name, or to thank him.

"If he wasn't there, I don't want to think what could have happened," she said.

Without a name, a number plate or an employer to track down the good Samaritan, Ms Tropea turned to Facebook to ask for help in finding the driver.

"I need to say thank you for helping us ... please help me find him," she wrote on Sunday afternoon.

Her post, with a quick snap of the driver, has since been shared by 30,000 people online, and seen by countless more.

"I've got 700 messages, people saying they might know him," Ms Tropea said.

She is now in the process of trying to contact the driver.

"I can't believe it. It was a long shot, but I believe in miracles.

"He could have sat back, but he helped us. I'm so grateful. There are some beautiful people out there."

Do you know the driver? Email joshua.butler@illawarramercury.com.au