According to an earlier story, the hard drive contained four-years' worth of the family's digital pictures. So, maybe because of their previous experiences with the DHS and law enforcement, they hid the hard drive to keep it safe. Maybe they worried that, if the police get possession of it, that could very well be the last they'll ever see of the undamaged hard drive and/or the precious photographs it contains.
That's pretty much the only innocent explanation I can come up with. Of course, thinking of not-so-innocent explanations is a lot easier.
This makes no sense to me because if all her pictures of her precious child were on a "hard drive" you would think she would down load them on to a disc, print them etc.
That would be an innocent person's instinct.
Something's really not right about these people - from the obvious to what we dont' know.