The woman said that when challenged, the youngster said he wanted to use the phone but then left. She called the police.
Mr Burne was quickly in the area and located the boy from a description of his clothing and the direction in which he'd been reported as heading.
It was not the first youngster Mr Burne had been called to check out recently.
A 10-year-old boy was identified as being involved in six window-smashing incidents in Tamatea during Easter.
The night after he was interviewed about one of the incidents, he went out on another smashing spree.
Earlier in March, Mr Burne was alerted to two boys in their early teens acting suspiciously - "roaming around" the Onekawa industrial area, which was the target of five burglaries that month.
The pair managed to elude him and a community patrol volunteer.
Later it was discovered a cashbox was missing from a business in the area where they had been spotted.
The Onekawa industrial area was seen by some opportunist burglars as "easy pickings", Mr Burne said, adding there were several individuals and groups active there.
The long, warm summer had been a factor, with many businesses leaving side doors and entrances open to catch cooling air - they were often in unattended areas and allowed thieves quick, often unseen, access.
Burglars could get in, have a quick look around and grab anything close at hand in a matter of minutes.
Mr Burne said calls reporting any suspicious behaviour were vital.
In one incident he was called by someone who saw a young man making off with a car rim from a yard. He was seen getting into a car and it was traced by police. The car was found to be full of scrap metal.
The owner was charged with burglary and the car rim offender charged with theft.
"Stealing a car rim would usually lead to stealing something else, which in time could lead to stealing something more substantial," Mr Burne said.
The call may have prevented what he called an eventual "decent rip-off" at the premises, or someone else's premises.
"Thanks to those who rang this in. I believe you made a difference."
It is understood the 12-year-old would face no charges and had been returned to CYF's care.