If LE was able to trace a cellphone to the trail, they’d also have enough information to also know who was the service provider. They’d be able to obtain a name and address and a treasure trove of historical information including other calls to friends, relatives, employer etc.
Had they been able to successfully do so, I don’t think they still be holding PCs asking for that “one tip”, starting in a new direction more than two years later.
BBM
So LE has received more than 42000 tips since the muders, but are still asking for that "one tip" that will lead to an arrest.
-They may have some DNA from the bodies or crime scene (but obviously no match in CODIS).
-They removed things (such as leaves) from the crime scene which may be evidence.
-They may have footprints leading to/from the bodies.
-They have a video recording of BG walking on the bridge.
-They have an audio recording of BG's voice.
-They may have the entire crime recorded on Libby's phone (in audio or video or both), or at least enough of it to get a sense of the flow of the crime.
-They know COD based on the autopsy and CSI.
-They know if one or both of the girls were SA based on autopsy/CSI.
-They know TOD based on the autopsy/CSI.
-They should know what type, if any, weapon was used in the attack based on the audio/video as well as autopsy and CSI.
-LE know the timeline of the crime based on KG's report of when/where she dropped the girls off, the 2:07pm SnapChat photo of Libby on the bridge, and the girls failure to respond to DG's messages starting at 3:11pm.
-LE have a witness that 'reported something that needed to be reported'.
-LE made a sketch of BG within 3 days of the murders that is now giving a more accurate face to this crime.
-LE have awareness of a vehicle parked at the CPS building that may be linked to BG, and may even know the make, model, colour and registered owner(s) of said vehicle.
-LE have established (through profiling and/or investigation) that BG is local/has ties to Delphi.
-LE have investigated the girls social media accounts.
-LE have investigated and ruled out local RSOs and other POIs such as DN.
It seems like they have so much, yet so little all at the same time. Short of a confession or someone calling in to report that they lied about an alibi, what could the "one tip" be that they are looking for?