"You don’t know that it has been tipped off, Bob. Think of how the CDC would track down disease spread. Lots of detective work, mapping of contacts, logical extrapolation, and so on. They can’t find Bob with a bulky backpack anywhere, so it’s logical to assume you’ve either gone into hiding or found a different way to get around. They know where you left the infrastructure, because they have a failed use of Natasha’s card. From there, it’s just a case of working outward. And given Quinlan limitations and the geography of Heaven’s River, they can concentrate mostly on east and west."