Maybe it hit a rib? But it sounds like the bullet did it's job in opening up and not passing through thus transfering the energy to the deer. Did she go down then get up and run?
The fallacy that FPE is "transferred" is simply not correct and not possible. A bullet strike is an inelastic collision and as such most of the energy is transformed into other forms of energy Mostly Thermal energy.
Before the wide spread use of the electronic chronographs ballistic pendulums were used to determine the velocity. A bullet of known weight was shot into the pendulum and the distance the pendulum swung was measured. The swing distance of the pendulum measured the amount of "MOMENTUM" that was transferred (not energy) with the bullet weight and the momentum transfer now known the velocity needed for the amount of momentum transferred could easily be determined.
After the velocity was determined then and only then could the FPE be "Calculated". Energy is not tranfered and therefore can not be measured only calculated
