But Judge Nicki Chapman - glammed up in a black leather dress - told the crowd that Zoe had laryngitis and tonsillitis and would not be able to perform.
"Zoe is in her dressing room crying her eyes out so I want you to give her a massive aaah to make her feel better."
Gareth and Hayley duet
Hayley Evetts stepped into Zoe's shoes for a duet with Gareth and the other seven finalists joined them on stage for a big band number.
A spokesman said Zoe should be well enough to perform in Sheffield, the next stop on the UK Pop Idol tour.