Because reporters are constantly moving about and in regular contact with a variety of people, I can imagine having their phone nearby is a big boon to the trade.

Does anyone know if portable, packable, and sufficiently effective, Faraday cages exist. Effective enough to block all incoming/outgoing signal?

In that case they could deposit their phone in the pack at a random location heading to the meet-up, then remove it at another random location later [without having to leave it behind].