Garner, who was staying in the Harbour City with Swans onballer and former Kangas teammate Ryan Clarke while North had their mid-season bye, is alleged to have broken a man's nose at a popular pub in Sydney's eastern suburbs.
Swans officials said in a statement that while Heeney witnessed the alleged scuffle, Clarke had already left by the time it occurred.
Sydney footy boss Charlie Gardiner said Heeney stopped the incident from escalating further and lent his assistance to the other man involved.
"Both Isaac and Ryan kept the club fully informed about what occurred over the weekend," Gardiner said.
"Isaac should be commended for diffusing the situation and offering support to the other party."