Australian Cheika was coach of the Wallabies between 2014 and 2019, but after initially taking on a consultant role, took over Argentina fulltime in March.
He masterminded a seven-try romp for his side against a depleted Wallabies, Argentina's biggest ever win over Australia and their largest in the Rugby Championship.
"I love these guys, they're my crew now," Cheika said. "I was up on the last try, cheering. But then I started crying because I know I probably shouldn't be doing this. It was a bit confusing for me, personally.