What to do if I find a piece of a different type of kibble in my dog's food?

I feed my dogs the Nature's Domain Grain-Free Salmon from Costco for several reasons, but mainly because they miraculously aren't allergic to it. I was feeding them dinner just now and discovered a piece of kibble that does not look like the other pieces at all. The kibble generally looks like imperfect circles, is a dark brown color, and has a distict texture to it; where this mysterious piece is bone shaped and is a very light brown color. If this doesn't sound like a big deal, then your dog probably isn't as allergic to everything as mine are. By buying this food, I'm putting trust in the company. Does anyone else find this incident to be unacceptable? I get its a big corporation and mistakes are made, but in this era of accidental deaths and recalls they need to pay closer attention to wtf they're doing. What if it was the exact type of food that my dogs cannot eat? This really upsets me. Has this ever happened to anyone else, finding a piece of unkown kibble in your dog's food bag?