In reply to PaulGraham:
> yes, I know they shouldn't have phones on DoE, but maybe it was sealed in a bag for emergency use only
There's no ban on the use of phones for DofE. They are accepted as useful organisational and emergency devices. BUT they are only supposed to be used for expedition use; they are not to be used for phoning home, chatting to their friends, posting on Snapchat, etc... They are also not to be used as a replacement for proper supervision in the field; supervisors must still meet the groups regularly to check on their condition.
We let our groups carry their own phones for recording purposes (photos, videos, etc), knowing that, in the event of their issued team phone not working, they could use their own phones to contact us, possibly mitigating the problem of network coverage. But we're strict about the external contact, and trust them not to. On the whole our groups live up to that trust.
Given the circumstances of the group, as you describe, I too think they did the right thing.
Post edited at 13:02