advice please

i need some help, i just don't know what to do i have a 17 yr old daughter under a full care order she has recently found my siblings on Facebook , im disturb by what my daughter has said about her foster carers... she has been going out alot lately but always goes bck home at night, i have had no contact with her apart from our contact we have every 6 weeks, with social worker, today at 10 my house was turned upside down by police looking for her i was at work, my son opened door they barged in pushed him out way and started searching for her than police came to my work and said your daughters been missing since 9 30 any idea where she is. i had been at work since 9 this was at 11 30 my sister manage get hold of her on phone and she said she gone home but no one in she waited there for 4 hrs, so far and as far as i know still waiting why would carers say shes missing after 2 hrs and go out anyway, my sister told her call police herself as they out looking for her anyway and she said she scared as foster carer told her they will lock her up, they tell her she has to cook her own meals but not allowed use the cooker they call her fat so she stops eating she always not hungry, and they have told her that her birth family don't love her im really worried i just don't no what to do and she also told my sister she went home 5 mins late other day and she refused tell them where she was so they grabbed her threw her out in garden till midnight and they told social worker she walked out, any advice please im desperate