When LE gets a data dump from the cell towers, as they typically do, and say the abductor(s) also has a cell phone, the LE can match pings triangulated to MTs last known location with any pings from any phones in the same near vicinity at the same time. This is possible by a method of what amounts to reverse triangulation. For instance, you could use the records to find find all phones with a certain ping speed, given phone and carrier and with a margin of error, that would match MT’s last pinged location to a particular tower. You would then do this for two more towers. You then combine the data of all the sources, look for the appropriate overlap, and see what phones match. Even given a margin of error, it would give you a reasonable list of phones to isolate. Of course, somebody could be using a burner phone or a stolen phone.
Everything done through the towers is logged so, for example, LE could do a regression analysis to find phones that are not usually in the area based on the numbers they find in their investigation, which could indicate some outsider suspect. With a town of 1500, it would not be too difficult to isolate a small pool of people of interest this way.