Besides predation being how nature works there is frequently no way of knowing if the fawn was killed by the predator or simply scavenged after dying of natural causes.OP, I know how you feel. Just nature working as designed though.
Studies have shown that a high percentage of fawns, ranging from 12.2% to 92.9% depending on the winter and spring food supply for the doe, that die of malnutrition from being born under weight within the first few days of life. That means even in the best of habitat and environmental conditions about 12.2% of the fawns will die of natural causes before predation even becomes a factor. That natural death rate increases to as high as 92.9% as the habitat and/or winter/spring environmental conditions decline.
With those high natural fawn mortality rates just finding the remains of dead fawn doesn't really mean the fawn was killed instead of just eaten by the predator who found it.
Even during the fawn mortality studies it was possible to assume a fawn died from predation when in fact it may well have died from natural causes then just eaten by one of several different predators. Having been on some of those mortality investigations I can attest to the fact it was often hard to say for sure.