Well, any Policeman will tell you most children abducted are killed within 48 hours, so, yes, the chance of her being found alive are every remote, and sadly, it is common for Parents to be convinced they would know if their child was dead, but it is rarely the case.
Concentrate on their family yes but never forget her of course.
I guess they are carrying out this investigation in the hope of catching the people who took her and preventing others from being taken, but there comes a time to judge the cost against the likelihood of Success, and have we reached that point?