Information about Turnbull's whereabouts and whether it was properly disclosed formed the basis of Mayer's appeal.
Mayer's lawyer argued in front of Justices Rhys Harrison, John Fogarty and Robert Dobson in March that prosecutor John Dixon had earlier misled both the court and the defence when he said the Crown was unaware of Turnbull's location.
The defence counsel claimed that this "misconduct" was egregious enough to justify a retrial.
Mr Dixon received information on three occasions about Turnbull's possible whereabouts in 2011 and 2013 but doubted its accuracy and did not think it would help Mayer's defence.
"Much more likely, any evidence Mr Turnbull sought to give would inculpate Mr Mayer," Mr Dixon said in an affidavit.
"I always doubt the information I had received about possible places where Mr Turnbull might be. I did not consider the unverified tip offs as to these possible places to be relevant or required to be disclosed," he said.
The three Court of Appeal judges exonerated Mr Dixon of any suggestion of misconduct.
"We are satisfied that the prosecutor was under no obligation to disclose this information... moreover even if it had been disclosed, there is no reasonable possibility that the information would have affected the reliability of Mr Mayer's convictions.
"In our judgment the information would have had no effect whatsoever on the overall fairness of the trial process," the judges said in their decision today.
Justices Harrison, Fogarty and Dobson rejected the appeal against conviction, as well as throwing out a challenge to the length of Mayer's sentence and the minimum period he must serve in jail.