So it's "unclear" where the mother is or what happened to her. Let me suggest two likely scenarios for a custodial father who had no problems torturing his own little girl:
1) He killed her and hid the body very well; or
2) She fled for her life and has "disappeared" in order to stay alive
http://www.mirror.co.uk/news/world-news/chinese-girl-torture-father-arrested-1888845
Chinese girl torture: Father arrested after 11-year-old daughter is found with mouth stitched with fishing cord
14 May 2013 15:49
Xiao Li was also forced to kneel on broken glass, hung upside down and beaten with sticks and had her head dipped in boiling water
An 11-year-old girl had her mouth stitched up with fishing cord and her head dipped in boiling water during a horrific campaign of alleged abuse by her father, according to reports.
Little Xiao Li was forced to kneel on a floor covered with broken glass, hung upside down and beaten with ropes and sticks and had her skin pierced with sewing needles.
The malnourished child's unimaginable ordeal came to light this week when she was discovered walking along a road in the town of Shichang in China's southwestern Guizhou Province.
Photographs from the hospital she was taken to show scars all over her body, while her hair is unlikely ever to grow back because of the temperatures it was subjected to.
The girl's father was arrested following the discovery of the girl.
The victim's grandmother, who is mother to the arrested man, told Sky News that she had looked after the child for five years before her son returned from working elsewhere in China.
Xiao Li is now recovering in hospital.
The costs of her medical care have been waived and the local authorities claim to be organising an extensive programme of psychological treatment.
Chen Yuefang, a local government official, said they are now seeking guardians to look after Xiao Li for the remainder of her childhood because her grandparents are too elderly to do so.
It is unclear where her mother is or what might have happened to her.