Another taxidermist horror story! I'm sorry about your situation. These things seem to happen more than they should and they should never happen. I was a taxidermist for twenty years and never had this problem. This would be a good time to remind folks about ways to try to avoid this situation when choosing a taxidermist.
It's a good idea to visit taxidermist studios BEFORE you have a trophy. This gives you time to shop around and plan rather than having to make a quick decision.
Obviously, you want to see some of the guy's work, but of equal importance is to talk to references, and don't be afraid to ask for names and phones numbers of former clients.
Be sure you get a contract which describes your mount as to species, size, etc.
Also it's a good idea to have the contract give at least an approximate date for completion. (I used to add a couple of months to when I thought it would be done. That way I had extra time built into the contract just in case I got behind for any reason. Hunters were delighted when I usually completed the work before the contract indicated.)
I hope your situation gets resolved to your satisfaction.