Irish singer Janet earned positive feedback from the panel on Saturday night's show and music mogul Simon gave her a place on one of the coveted six seats - only for her to lose it soon after.
Simon's bootcamp continued on Sunday night's show, and as the seats filled up, the competition was getting tense as he battled to choose his top six over 28s to go through to the Judges' Houses stage.
When mum-of-three Helen Fulthorpe took to the stage, she wowed the judges with her vocals, and Simon guaranteed her a seat. But with all six seats occupied, he was forced to make a swap.
Simon initially asked Lizzy Pattinson (Robert Pattinson's sister) to stand up, but following disapproving jeers from the crowd, Simon told Lizzy to take a seat again, leaving him to call Janet to be replaced by Helen.
In tears, a devastated Janet walked off stage where she was comforted by Dermot O'Leary.
Covering his face with his hands, Simon told fellow judge Cheryl Fernandez-Versini: "I wish I could start this day all over again."
Taking to Twitter last night (28 September) straight after the show, Simon told his 10.5 million followers that he made a mistake. "I should have kept Janet. My mistake," he said.
I should have kept Janet. My mistake.— Simon Cowell (@SimonCowell) September 28, 2014
Despite going home, Janet is keeping positive and says she won't be giving up on her dreams.
She wrote on Twitter this morning (29 September): "The love and support is REAL. Thank you so much. No giving up here, don't worry. I wouldn't know how to stop even if I tried."
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Watch Janet's arena audition in the video below: