On Monday, the Department of Children and Families released public records documenting a history between Dontrell's family and the agency.
Dontrell Melvin has not been seen since July 2011, and human remains have been found behind the house were his parents used to live.
In October, a Hallandale Beach Police Officer called a state child abuse hotline to report that Sierra said she had not seen her son in more than a year.
"She said she hasn't seen the baby in -- since July of 2011," the officer said in the recorded conversation.
The hotline operator asked what was going on with the case.
"I was just told that my Sergeant wanted me to contact you to let you know, I mean, she hasn't seen the baby since July of 2011. I mean, I don't know how persistent she was in seeing her child. She still talks on and off with the father but every time she asks about the baby he is just always making excuses and never brings the baby by. She doesn't even know, I mean, whether the baby is even alive or not," the officer said.
The call was documented but "screened out."
The Department of Children and Families said missing child cases are not under their purview and pointed to the police department as the agency responsible for investigating missing child cases.
Police told Local 10 the October inquiry was a custody issue, not a missing child case.
Documents released by DCF show subsequent anonymous calls to the child abuse hotline reporting drug use in the home of Brittney Sierra's mother, where Sierra was living with her other children. Another caller reported that some of the children were left unsupervised, and that at least one child wore days-old clothes and smelled.