Question about The Passage. I didn't see spoiler in title, so I'm putting in spoiler tags

Spoiler:
I'm going through a re-read (this time audiobook) of The Passage. Will someone remind me how it is that the FBI hears about Amy being with the sisters? I remember wondering about this in my first read and I must have missed it again when listening. It seems as though she was dropped off by the mom, but all the sudden the FBI is aware of where she is even though it was never reported.