A number of gun manufacturers do a great job of finishing their stocks but provide little or no protection, on the wood, under the buttplate. Some folks think that you don't need to protect this area and that's wrong. In your case, what I suspect, is that yours does have some protection but what that might be, would only be a guess on my part. I have see the normal finishes, Epoxy, contact or rubber cement and Wax. Again, all in an effort to weather seal this end. .....
I'd say to try a "little" heat and see if this loosens the bond. By the way, I have also seen the application of small brads or pins to hold the white spacer, to the stock. Might be a good idea to contact Anschutz and see if they can help. Please come back and let us know how you made out ..
Hang in there and;
Be Safe !!!