Robbie Hance, 26, will appear on tonight's (September 16) show, performing a cover of Damien Rice's 'Coconut Skins'.
However, the singer - who has spent six years sleeping rough on London streets - is said to have lost contact with X Factor producers for the last six days.
Producers have now launched a manhunt in order to locate Hance, but if he is not found within a fortnight, he will lose his place on the show, reports The Mirror.
A show insider said: "He's a fantastic artist and he blew everyone away at auditions.
"He doesn't have a phone and the only point of contact was through a friend. Producers last spoke to him on Monday but they can no longer reach his friend and have no idea where he is. It's a real worry.
"If he doesn't get in touch by the end of next week, then he'd have to kiss goodbye to any part in the show, which would be a tragedy."
Hance impressed the judges after his audition, with Tulisa Contostavlos telling him: "You look like someone that has been lost for a while and I think you need to realise the potential you have and how good you are."
Louis Walsh said: "I think you are a very talented guy but I don't think you have had a break in life and I think you absolutely deserve that."
Gary Barlow added: "You have got lots of talent and absolutely zero confidence and that is the only thing to work on in my perspective."
Hance reportedly grew up with his single mother in London, but was later taken into care at 13. He has been unable to keep a steady job and has been largely homeless throughout his 20s.
The X Factor continues tonight at 8pm on ITV1.