I will await the opinion of those more familiar than I with the ease with which ALL characteristic radiation from such a weapon could be stopped sufficiently that it would only be detectable by opening the container. I really don't know. But the possibility could raise some counter uncertainties by the senders. Presumably, they wouldn't do it if they thought there was ANY chance that one would be found before it or any of them went off. With the device in hand the sender becomes more likely to be identifiable to a reasonable certainty.

"It is not necessary to have hope in order to persevere."