With the possibility that Lena was kidnapped to "complete a set" in regards to children, I am hoping that increased Ramadan mosque attendance may lead to somebody hearing about a family that dropped out of sight mosque / social calendar wise after an unusual "adoption" etc.
To me, Lena's case seems vaguely similar to these unsolved kidnappings:
Every Theory About The Harlem Kidnapping Cases From 'Unsolved Mysteries'
Though all children are cute, the missing children were seen as being especially cute / attractive. They also both had the uncommon "pop eyed" physical feature that can be seen as desirable. Lena could also be seen as especially attractive, even when compared to other little girls.
With the NYC children, the police pursued every motive, including a "shopping list for an adoption" type motive. As with Lena, nothing panned out.