I'd tell him, you want the rug, and plan to take it to another taxidermist.... to have finished, see what his reaction is? if he lost it, stole it? sold it? figure out if it still exists, if it was lost, get your costs back....sue if you have to, not just the fee's you given him, but what it cost to replace....

My worry wouldn't be the license, but the rug, you can work out the details....not the first time someone lost their license/tag etc....