My first guess is that he lost your hide or screwed it up and is stalling till he can substitute it. Or he just plain lost it and wont face the situation.

I dont think you need a lawyer yet but going to the local JP or magistrateshould get his attention and hopefully some quick results. That bear has a monetary value even if you would never sell it and if the bear is gone or damaged, you can at least hit him hard in the wallet. The fact that you gave him no money doesnt matter. You put somethingthat has significant value to you in his care custody and control. He is in the business of accepting animals to mount and has a responsibility to keep it safe and return it to you.