Q - "Out of interest, would the network register a text that was being composed, but not yet sent, at the time of the collision with the crane ?"
A - Yes. Although the message itself hasn't yet been sent, there will be traffic on the network to inform imessage on the 'receiving phone' that a reply is being composed.
SS
According to the SB, there was a message received but 'not read'. Thats not to say that it wasn't seen
Dave
Actually, I think that's exactly what it does imply.
Seen, but not 'read';
With a smartphone, when you are sent a message, part of that message (or all of the msg if it is short) can be seen on the home screen without opening the conversation, simply by looking at the display. Until the phone/message app is 'opened', the message will be shown as 'unread'.
(however, we don't know what phones were in use!)