Others tweeted: "And our very own Delta Goodrem has a surprise in store... Ok, why didn't this happen?"
"But where is Delta Goodrem's surprise performance???"
The confusion comes as Boy George's songstress Diana Rouvas was crowned the winner of The Voice 2019, the first female contestant to win the singing competition since Ellie Drennan in season four.
Rouvas, 35, beat Delta Goodrem's singer Daniel Shaw to take the $100,000 prize money and a recording contract with EMI Music.
She first appeared on the first season of The Voice Australia in 2012, making it to the final eight with Nicole Kidman's husband Keith Urban as her mentor.
She finished fifth, but returned to the iconic contest this year at the request of Channel Nine producers.
Delta and fellow Voice coach Kelly Rowland stole the sartorial show on Sunday night in statement gowns with perilously plunging necklines, while host Sonia Kruger also flashed some flesh in a thigh skimming mini dress, Daily Mail Australia reports.