They were clearly unhappy, that not only hadnt they been able to complete their mission, but they had also suffered these many injuries, and also come across something like this.
If one looked at the whole scene and situation objectively, they would be able to see that these guys had unwantonly made a great discovery.
Unfortunately no one would be able to judge this situation objectively, and especially the Provincial Lord, who thought of this as a direct challenge to his authority.
Most importantly, things wouldn't have reached up to here in case these guys had done their job properly and they had deal with this place from the very beginning.
Of course, the fact that they weren't able to due to the difficult situation, and that barrier wouldn't be excuses in front of the Provincial Lord.