How will I know if Massachusetts DCF opens a case or not?

I was in an abusive relationship that I just left 2 months ago. He wasn't my child's father. Once she did see him try & strangle me, however, when the DCF social worker asked her if she's ever seen anyone hit her mother, her reply was "no". My daughter was never witness to any abuse other than that but she did hear us argue on occasion. How will I know if DCF opens a case or not?