Hypothetically possible, but your previous comment delt with the FBI being unable to trace a phone after simply inserting a new sim. Which is incorrect. They could easily trace it. Establishing ownership is another issue which was not part of your original scenario. Although I think establishing ownership wouldn't be that difficult based on whom the owner ended up calling and references to whom was called prior to any sim swap . Your mileage may vary
For instance, Barry has a burner he used to call his crew. Just check Barry's crew phones for similar numbers. Both before and after a sum swap. Most of his crew prolly would have fingered him anyway.
It was part of a post I made on a prior thread. It was rather lengthy and included more information on how it's done. Sorry if I misled. Inserting a new SIM alone would not work. Establishing ownership is obviously the key to tracking a burner phone.
There are a number of ways to get a burner phone not registered to oneself. The first would be to buy a used one at a flea market or similar. The second is to pay cash at a kiosk or pop-up (these are easy to find in some places, particularly in Mexico, but also in Los Angeles). Another is to do what my neighbor did - and steal credit card information from someone else, have it shipped to an address where you know the person is going to be moving soon. The phones purchased with my stolen CC information were sent to a Mailboxes Etc in Austin, TX (where my neighbors' daughter lived). The Mailboxes Etc did not have any information they could give the bank about who had once had that address, but of course, the investigation was not by the FBI. Ther
At any rate, there's no point in having a burner phone for illegal reasons if it was registered to you when you bought it.
I suggested in an earlier post that the easiest way for Barry to have one (I do not think he had one necessarily - although I do believe he had a second phone and that the FBI has that phone in their possession, IMO)...was to get it in Mexico. However, it would not be an iPhone and wouldn't be linked to the Morphew's joint iCloud account, so would not be able to track Suzanne's phone easily. I think he just used iCloud to see where she was, personally. She could have turned it off (took me a couple of tries, one needs to disable a couple of things), but then Barry would have confronted her and been suspicious.
Tracking one's wife through installing an app on her phone (perhaps in a hidden folder) would be possible with a burner, I suppose.
At any rate, sorry for the confusion. A separate cash based SIM purchase would not, by itself, make the phone untraceable. A cash-paid burner phone bought in Mexico would, though.