It's a good idea they're going nationwide. Thinking in generalities, people who aren't the parents or grandparents of a baby (and aren't the boyfriend of the mother or some other jealousy entanglement) tend to do it either to raise a child or to try to market the baby to other hopeful parents.
I can't think of a case (there must be some, I just don't know any) where babies were the victim of choice for a sexual predator kidnapper.
Working against finding her is the fact that she's completely unremarkable looking. She just looks like a plain ol' baby, could be male or female, no obvious features that are memorable.
Prayers they find her. It's looking dimmer.