Burner phones are traceable as well if you use them to contact others not using burner phones or to move money around in bank accounts connected to you. The difference is that Tylee's phone would already have access to Tylee's bank account, email, etc without the need to set up a new security login on a new phone and change all the passwords or use new email accounts. If Lori comes under investigation for a financial crime such as the theft of the money from Charles business account in Jan 2019, where is the probable cause going to come from to search for Tylee's phone hidden in a storage unit? They would take Lori's devices first I think. If Tylee's father left her a large sum of money (I think it was around $75,000?) and that money is being accessed by someone else using Tylee's phone it might become difficult to prove who was accessing the money. If Lori got a burner phone and started accessing Tylee's money then that would be more obvious and easier to prove it was Lori and not Tylee making the transactions and exactly when that started happening. And conveniently, someone could pretend to be Tylee and send texts with the phone number her family and friends already have and it's difficult to prove it wasn't Tylee. MOO.
ETA: Of course the big flaw in this plan to use Tylee's device is that Lori doesn't seem to have considered what would happen when people noticed Tylee was missing. Lori seems to think she can tell people Tylee is away at college and it would be believed. Sadly, it has almost worked because we don't know exactly when Tylee was last seen. But the search for Tylee and JJ has seemingly put the spotlight on other shady activities. I don't think the POI's expected this much publicity nor the amount of LE effort that has come about. We're not currently privy to many things LE knows but we know they have gotten multiple warrants that they would not be able to get without so probable cause. IMHO, the children being missing so has given probable cause to investigate other possible crimes.
