Most deer i thumped in the boiler room ( double lung) died within seconds. Average about 6 second or so.
Ruminants have a well established mediastinum. That is a membrane that divides the lungs.
If you only get one lung it can collapse & clot. The critter can survive with the other good lung. This occurs usually when it’s a straight down shot. The deer is directly below the shooter.
Thinking the same thing, they drop down almost instantly with no tracking needed.
