I hope they are checking out all reports of stolen white trucks. I think the Fredericksburg getaway was a mid size dark sedan, so I hope they're looking at the car rental agencies and stolen car reports too.
Again these guys want to remain as invisible as possible and the easiest way is to buy a truck/van, at least for the first few hits until people start to notice.
What they *could* try, technology permitting, is a cross reference of recent short term motel stays in the greater area (say, 100 mi. radius if possible) with recent truck/van purchases, recent car rentals, and recent credit card gas purchases. Do a cross check by name and social security number instead of just credit card number (to catch multiple credit card holders). Most people use credit cards these days and those who don't tend to attract unwanted attention, so these guys probably used credit cards too. They might have bought the van with cash as an exception so such a search might not count on that particular item showing up in the results.
These guys are using the safety in numbers technique of avoiding detection. Computerized methods are an efficient and economical way to root them out imho. Also I imagine that the authorities may even be busy doing this kind of search, even as we type...
Relying on locality alone as a guide to casework sounds to me about 30 years out of date, something that might look good as a technique in "Hunter", "Rockford Files" or "Dragnet" but perhaps less than appropriate in today's post-industrial info age...