Im confused by the question(s) here.
1. You assume the model is stolen
2. If it is stolen - you want it free?
Did you contact the artist or support? Why come here and accuse someone first without speaking with the author?
If you are using stolen assets in your game, knowingly or unknowingly then you are already on a bad path which will come back to bite you. Its hard to entirely understand from your very limited wording but that's what I understand from this. Correct me if I'm wrong please.