A young girl discovered her baby brother dead in a locked hot car

Jone died after being accidentally left in a hot car. Photo / Channel 9

A Sydney grandmother remains riddled with guilt after a momentary lapse of concentration saw her leave her daughter's 23-month-old son locked in a hot car.

Valerie Rowlands was babysitting on February 3 this year when she returned home from a car trip with her six grandchildren. After bringing the brood inside, she sat down to rest and dozed off, waking up with a start some two hours later.

"I thought, 'Oh, my god, the kids' and got up and went to the window," Valerie told Channel 9's A Current Affair. "I said, 'Where's Jone?'"

When it was clear the toddler was missing, she screamed for her young granddaughter to check the car parked outside.

"I said, 'Oh, run, go quickly and have a look' then she came back inside and said 'Nan, he's in the car'. She said his eyes were looking at her but he's not talking. And, oh …"

Jone's grandmother Valerie was minding him when a momentary lapse of concentration saw him accidentally left in a hot car. Photo / Channel 9

Samantha was at a football game when she noticed a missed call from her mum, listening to the hysterical voicemail alerting her that something terrible had happened.

"I listened to it and all it said was 'I think we've lost Jone — Sam, the ambulances are here'. And then by the time I got there, the detectives confirmed he passed away."

News crews at the scene captured the heartbreaking sight of Samantha breaking down in the street after being told Jone had died.

It was a 30-degree day but inside the vehicle the temperature likely reached 60 degrees.

The heartbroken mother and daughter decided to tell their tragic story as a warning to other parents about how easy it is to become distracted.

"All sorts of stuff can take your mind off your child," Samantha told the program.

In the past decade, eight children in Australia have died in hot cars and some 5000 have been rescued.

Samantha Rowlands posted a photo of her and her son following his tragic death. Photo / Facebook

Christine Erskine from the organisation Kid Safe said parents should form a habit of checking the back seat every single time they get out of the car — even if their children aren't with them.

Erkine suggested putting a handbag in the back seat as a reminder.

"There's usually some change to your regular pattern that puts you in a different frame of mind," she said.

Rather than be torn apart by the tragedy, Samantha said it made her relationship with her mother stronger.

"I don't blame her," she said.

"Look, I've lost my baby and no-one else should. It was just an accident, what happened, and at the end of the day, and I love her. She's still my mum."