The Department of Children & Families child abuse hotline is accustomed to unsettling phone calls, and this arguably was one.

It was last October. A police officer was on the line. He said a Hallandale Beach woman, Brittney Sierra, was claiming she hadn’t laid eyes on her own 1-year-old son in 15 months. The officer said the woman “talks on and off with the father,” Calvin Melvin, “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 dead or alive.”

The report of a child missing 15 months triggered no alarms at the child abuse hotline. As DCF officials explained this week, they consider “missing persons” a police matter and not a child welfare issue.

For his part, Hallandale Police Chief Dwayne Flournoy said his department judged the situation a custody dispute, if anything — and he assumed DCF would sort things out.

Neither agency did anything more.

As it turned out, Dontrell wasn’t hard to find. Last week, after questioning both parents, police swiftly unearthed a tiny skeleton from the backyard of a home in which the couple lived until a year ago. Police have not yet positively identified the remains as Dontrell, although that is the expectation.

While there’s no evidence the agencies’ inaction led to Dontrell’s death — he was presumably already dead — it did leave Sierra’s two other children in an unsafe environment. After the arrest of Dontrell’s parents last week, so far just on child neglect charges, those children have been placed in the care of the state.

The grim discovery behind 106 NW First Ave. has, once again, left state child welfare administrators explaining decisions that critics of the agency call questionable: Less than two years after the death of Nubia Barahona — and more than a decade after the disappearance of Rilya Wilson, who prosecutors say was killed by her caregiver — DCF ignored a report that a small child was unaccounted for, and possibly dead. In both of the prior cases, a task force urged the report to act with greater urgency when faced with a report of a missing child.

“We don’t seem to be learning from what’s occurred,” said James Sewell, a former Florida Department of Law Enforcement administrator and DCF consultant who sat on two panels that studied scandalous child deaths, including that of Nubia, who, police say, was killed by her adoptive parents in early 2011. “Obviously, these people forgot what we learned from the past.”

Said DCF Assistant Secretary Pete Digre: “We are taking this thing very seriously. We are looking at every way we can to improve and enhance common sense in decision-making.”

By the summer of 2011, when Dontrell was last seen by someone other than his parents, his extended family already had been the subject of about 30 calls to the DCF child welfare hotline. The details of those cases are unknown, as DCF will not release the records.

This much is known: At least two privately run agencies that work with troubled families in Broward County were visiting the home of Dontrell’s grandmother, Renee Menendez, in 2011 and 2012, when Dontrell’s mother and her children moved in with Menendez blocks from their former residence.