Karen Gudelj detailed her family's love for her long-absent son at an inquest into what happened to Mr Barnes before he vanished in the Hunter Valley region of NSW on November 13, 2016.
"Zac respected everybody and he deserves to be respected. If Zac has lost his life, we deserve to be able to bury him and remember him," she told the Lidcombe Coroner's Court.
Mr Barnes was seen acting distressed and angry in the days before he asked to get out of a friend's car while on a drive to Thornton railway station.
The Metford man was last seen running off along a dark road into bushland. He was reported missing on November 14 but despite extensive searches has not been seen since.
Coroner Carmel Forbes has been tasked with determining whether Mr Barnes has passed away, the manner of his death, and whether police did everything they could.
On Wednesday as the three-day inquest concluded, Mrs Gudelj described her son's life as a cute toddler, her "little protector", a boundary-testing teen and student who wanted to become a doctor.
As she spoke, photographs of Mr Barnes as a child playing in the pool, at birthday parties and smiling with his siblings were shown in the courtroom.
In year 10, his grades fell. He eventually wanted to quit school but worked hard to become an apprentice bricklayer.
"If I can just say to any family out there, Zac's life turned very quickly and I think a lot of it is because he wanted to be that popular, social kid," she said.
The inquest previously heard Mr Barnes used illicit drugs like ecstasy and LSD and was known to drink and party with friends.
In March 2016, Mr Barnes had an argument with his mother who wanted to charge him board for staying at home.
Mrs Gudelj described how her son had broken down and was sobbing in his bedroom but refused to say why he was so upset.
"I've seen stuff, I've seen stuff, I can't get it out of my head," he told his mother.
"He felt that if he told me he would get us into some sort of trouble," Mrs Gudelj told the court.
She also said someone had broken into their home after her son disappeared and had stolen items from his bedroom, which she believed was an attempt to make it seem like he took some items and ran away.
However, the individual took his brother Cody's clothing and failed to take items such as Mr Barnes' watch and Converse shoes.
The coroner also heard from Mr Barnes' employer Alan Kirby and friend Joe Robinson about arguments he was involved in the day before his disappearance.
On Wednesday Mr Kirby said he did not remember firing Mr Barnes on the day the apprentice bricklayer had an altercation with another employee while intoxicated at work, despite this being in his 2017 statement to police.
A friend Joe Robinson said on the day he disappeared, Mr Barnes got into another argument with a friend who he had stayed with for a few nights.
The teen had not contacted his parents for days before he was found at his mate's place.
When pressed to contact his mother, he got upset and asked for a ride to Thornton station where he made the fateful decision to run into the bush.
Ms Forbes will hand down her findings at a later date.
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