Vaauli held the owner down while his co-offender grabbed $1600 worth of cigarettes, then the pair made their escape.
But Vaauli was able to be identified thanks to security camera footage.
"As he jumped across the counter, police have been able to get an image of him that basically looked like an excellent selfie," a police spokesman told the Herald.
He was seen by the off-duty officer a short while later wearing the same clothes he'd committed the robbery in while he waited to catch a bus in the nearby suburb of Kilbirnie.
A police spokesman said Vaauli was spotted by an off-duty police officer a short time after the robbery, wearing the same clothes he had committed the offence in.
Vaauli appeared in the Wellington District Court this afternoon for sentencing.
Defence lawyer Brett Crowley said the co-offender had escaped conviction because he wore a "disguise", and so couldn't be identified on the camera footage like Vaauli had.
He said his client was remorseful and had made a "frank admission" that he was the one to hold down the shop owner, rather than his co-offender.
Judge Bruce Davidson said aggravating features of the offending included that the victim was confined and vulnerable, and that there was a degree of planning, "even at a fairly rudimentary level".
Mitigating features included Vaauli's young age, lack of previous convictions, and his "inherently good prospects of rehabilitation".
He said a pre-sentence report was "favourable", and that he agreed with the probation officer that giving Vaauli community work to carry out would expose him to "older and more ingrained criminals".
He sentenced him to eight months of home detention, with six months post-release conditions. Vaauli must also pay $500 reparation at a rate of $5 per week, which was what Judge Davidson believed he could "realistically" afford.
