If it were me, I would demand the taxidermist buy a new cape and remount the deer or pay for another taxidermist to remount it. If he doesn't make it right go the the dept of Ag who issues the taxidermist licenses and report your problem. I hope you have photos of the deer before the taxidermist got his hands on the deer so you have proof the cape was not damaged when you gave it to him.
When you are up to your butt in alligators, it is hard to remember your intent was to drain the swamp. Stay focused!