Former "X Factor" contestant Simone Battle's suicide has stunned her father ... who says the "G.R.L." singer never once let on that she was suffering as she got a taste of success in Hollywood.

Anthony Battle tells us he and his daughter hadn't spoke on the phone in a few weeks ... but they texted every day and she seemed to be doing just fine.

In fact, he says Simone was excited about where her career was heading. G.R.L. had recorded and released a song with Pitbull earlier this year.

We're told close friends of the 25-year old singer spoke with her via text the night before her death -- they also didn't sense anything was wrong.

When we asked Anthony if Simone was battling depression ... he said he was unaware of anything like that, but acknowledged ... "It's possible she may have had an invisible disability."

Anthony tells us Simone's boyfriend discovered her body in her bedroom ... but he doesn't suspect foul play.

An autopsy is scheduled for Sunday.

US singer Simone Battle took her own life on Friday, September 5, 2014 after she found dead in her Los Angeles home, reports say.

Law enforcement sources tell TMZ, Simone was found hanging on a rod in the closet of her bedroom. Her body was found by her boyfriend.

The 25-year-old singer, who rose to fame on the US version of ‘X Factor’, was a singer in the girl group ‘G.R.L’ (a reboot of the Pussycat Dolls).

'I am so sad to hear about the news Simone Battle has passed away. She was such a fun nice person. It's such a loss. Rest in peace Simone', X Factor creator Simon Cowell wrote on his Twitter.

Battle’s autopsy has not been completed yet, L.A. County Cororner's Office says. The Autopsy will be carried out today (September 7, 2014).

The singer’s father says his daughter’s suicide has ‘stunned’ him as Simone never for once showed any signs that could raise major worry.

Weeks ago, US actor Robin Williams also committed suicide in his California home.