You don't seem to understand the underlying problems.
Even if they did buy the turbosquid model, it doesn't allow commercial use, they should have contacted the original artist in the first place. But like it is stated in the response he got, the model came from a free source, thus not turbosquid.
Ultimately it's the developer's responsibility what source the model came from. They can reprimand the artist later, but that's an internal matter, it still doesn't justify what the contract artist may or may not have done and how any model is used or credited in the game. Outsourced models are still supervised by staff artists, so it should've been caught sometime during development.