Hassan said she saw the toddler in the car and headed for the church, thinking his mum or dad must be inside - but had no luck.
"So I stayed with him to see if anyone came to get him. No one showed. We were going to take him home and call police but a lady across the road stopped to see if we were okay."
They used the lady's phone to call the police, Hassan said.
Hassan has a daughter of her own.
"I just thought of the mother and how I [would have] felt if it was me," she said. "I wasn't going to leave his side ... anything could have happened if I didn't stop and go back."
Police said the vehicle was located abandoned on Rimu St and the child was found inside the vehicle, "unharmed and reunited with his mother".
The vehicle was abandoned about 1.5km from where it was stolen. Police were unable to confirm who had found the child.
The boy's distraught relative took to Facebook to plead for help tracking down the young boy, who is turning two next month.
The man posted about the incident on Rotorua Buy Sell Swap and Deals, offering a reward to whoever could bring the boy back that night.
He wrote that his former partner had parked the car outside a dairy near Rotorua Boys' High School, when it was stolen.
"Please any details or anything will help, all we want is our son back so we can be at ease.
"Who (sic) stole it has a big fat build."
In a statement police said they were speaking to witnesses and making enquiries to locate the person responsible for the vehicle's theft.