This is a critically important aspect of investigation IMO. With LE knowing Mollies digital path, presumably from her cell phone pinging the towers (along with Fitbit), couldn’t LE then reverse engineer Mollie’s precise areas & times on that path to determine if there was another cell phone pinging from those same areas/times? Assuming perp too had a phone (which we don’t know & quite possibility a false assumption), seems LE could then home in on the perps device. I have to believe with today’s technology & FBIs resources, some software engineer could run an algorithm to weed out any false positives to determine what other device(s) crossed Mollies digital path at the time she went missing. Given how rural that area around Brooklyn (ie pig farm), there wouldnt/shouldnt be many devices pinging from that area at precisely the same time/location that Mollie’s phone was pinging. I believe this could help home in a potential suspect(s)... (assuming perp too was carrying a live phone at the time). Just MOO.