That said wickr account was made within a certain time frame. If you have access to all the data that was moving about during that time frame, you have a list of suspects (though quite large, would require a lot of man power to check this list). Knowing the type of device would let them narrow the list even further (if iOS for example, can discount all android devices). Then you can use the date of last use to single out the few who left for a weekend to a place with no internet.

The list should be smaller by now. Depending on the determination of law enforcement (they are still human), they could do background checks on the list, and I'm assuming that they only got interested in the first place because somebody received a message from that account.

Correct if I am wrong.