The men, Peter Welsh, 32, and Dwayne Doolan, 31, allegedly tried to make the best of their mistake, and staged an impromptu hold-up at the fast-food restaurant in the town of Beaudesert, southwest of Brisbane.
They escaped with A$2,600 (£1,700) after threatening staff with a metal bar in the New Year's Eve robbery, but were then arrested and charged after a raid on Mr Welsh's home.
The pair of thieves were making their third attempt to rob the jewellers. They had previously attempted to smash through the front window.
When that attempt failed they then tried to get in through the back doors, but instead found themselves in the neighbouring Animal Welfare League Opportunity Shop.
On that occasion, they again tried to make the most of their situation, allegedly stealing a charity box containing $50 (£32).
In their latest attempt to target the jewellers, the pair broke into a lavatory block at the rear of the line of shops, police said, and used an iron bar to make a hole in the wall.
When their crawled through the hole, they found themselves surrounded by chicken nuggets rather than diamonds.
Police prosecutor Sergeant Damian Summerfield said at Southport Magistrates Court that they then threatened staff with an iron bar.
"One female staffer opened the safe and they grabbed lots of cash," he said.
Mr Welsh is charged with armed robbery, stealing, burglary and attempted burglary while Mr Doolan is charged with robbery and stealing.