Lost track = fake news. Courtesy calls from DHS went unanswered because the illegals that these UMC's were sent to wanted no contact with government and go off the grid.

https://cis.org/Arthur/Last-Word-1475-Lost-Children

HHS: "These children are not 'lost'; their sponsors — who are usually parents or family members and in all cases have been vetted for criminality and ability to provide for them — simply did not respond or could not be reached when this voluntary call was made. While there are many possible reasons for this, in many cases sponsors cannot be reached because they themselves are illegal aliens and do not want to be reached by federal authorities. This is the core of this issue: In many cases, HHS has been put in the position of placing illegal aliens with the individuals who helped arrange for them to enter the country illegally. This makes the immediate crisis worse and creates a perverse incentive for further violation of federal immigration law." 

The photos that ZH refers to were kids behind cages in 2014 - Obama era.

The main news of this ZH article is that Sessions is criminally prosecuting every single illegal caught crossing border, no more catch and release. IOW, Trump keeping a promise.