I have NEVER in my life heard of a true confirmed double lunged ANYTHING going 200 yards. His shot was not what he thinks.
Heart shot animals can run a bit further than a double lung but even then 200 yards is farther than anything I've heard as well.
They just don't get that far before stopping and succumbing to such injuries and loss of blood or air.

He quite possibly hit a bit low and back of the heart area catching the nearside lung only. Thats an animal that will bleed well with lung blood but can cover some serious ground.

All I can say is that you need more manpower to search that marsh and surrounding areas. Hard hit animals can be prone to sudden changes in direction and many times just aren't where you expect them to be.
IMO you need to skip the hunting tomorrow and do more searching.