It certainly sounds bad. The US government has lost track of 1,475 undocumented immigrant children; an official admitted as much during a Senate committee hearing last month. Fairly, that admission has spurred widespread demand for more agency accountability.
The problem, as the Washington Post notes (paywall), is that many of those missing kids may well be with their parents or families, and they may have gone off the grid deliberately to avoid Immigration and Customs Enforcement (ICE) authorities. Tracking them down could end up endangering more children and families.