@Mari38677 I chalk up damages to linens to the cost of doing business. If this is the first time that you have had a duvet damaged, congratulations on having had good guests!
What is the extent of the damage? A tear? An unsightly stain? I have actually "repaired" a damaged duvet cover by sewing a patch over it -- the patch was a decorative square with a drawn-on design -- looked like I had personalized the duvet. Or I just chuck it into the rag bin or mark it with a fat sharpie as a "DOG SHEET" for guests to use as a furniture cover for their dogs (even though I do ask for no dogs on furniture, due to guests who treat their animals like children, dog sheets save me a lot of headaches and doggie lovers tend to use them).
I have never bothered a guest about missing pillows or damaged towels, linens or items under $100 unless I can prove maliciousness. I do have a slush fund for damages, and I shop a lot of sales to find duvets, linens and other items to rotate into the property as needed. That includes hair dryers, small kitchen tools, dishes, flatware, etc.