Cher was "traumatized" when she realized she would never hear her daughter's voice again.
The 64-year-old singer begged her son Chaz Bono—who was born a female named Chastity and began gender reassignment surgery around three years ago—for a copy of his old female answering machine message after becoming "hysterical" when she called and reached his new voicemail.
She said: "I was hysterical one day because I was calling Chaz's answering machine and I realized it was her old voice, and then I said, 'Chaz is there a way I can save it because I will never hear that voice again?' And there wasn't, it was gone.
"That's the most traumatic thing that has happened to me in this whole thing—hearing her voice and knowing I'll never hear it again.
The "Believe" hitmaker also admitted she avoided seeing Chaz—whose father is the singer's late husband Sonny Bono—for a long time after he began treatment because she was so nervous.
In the new documentary Becoming Chaz, she admitted: "I was so nervous. I hadn't seen her and I was putting it off.
"My boyfriend finally said, 'This is crazy, just do it.' I said, 'I'm so terrified of what will happen. If I don't recognize her, what will happen?"
Cher also admitted she still doesn't feel "comfortable" referring to her offspring as "him" rather than "her."
She added: "At some point, I'm gonna have to start calling her 'him.' It doesn't seem comfortable to me yet. Actually I just can't remember and I guess I'll start forcing myself but I'm not sure she cares."