It's fair as it's only a cosmetic thing. The coating doesn't impact performance or anything. You just see fingerprints. Plus samsung doesn't warranty wear items. Such as the body and scratches that might occur. If you really need it back, amazon probably sells some or you can use a screen protector with it
If its worn off for some reason, this will be wear and tear. If its not been applied properly from new or some issue when you get it. Then that will be a manufacturer defect and come under warranty. I've had so many phones over the years, but not had that issue. It's normally quite robust and wonder what happened for it to wear off