True, but once in a while when you capture a scout you do find out who he was sent by. Obviously we wouldn't trust his word, would we? So if it is possible to find out which noble he was sent by to some extent, then the scout must have something in his possession to prove this or a letter from his noble. Perhaps just raise the chance of finding out who the scout came from if it was from an allied noble. If that does occur, the scout returns to the allied noble.
Nope, because that was in Helpline and not Feature Requests 
He was posing a question while I am suggesting a feature tweak.
It is a known fact in the BM world that torture produces the truth. Considering that, how do you think we find out which noble sent the scout? When you don't find it the scout died from the torture before the desired result was reached.
