I mean was it alive or dead? Certain small bugs like that aren’t uncommon to find in dry goods. Things like flour and grains have an acceptable level of bug ‘parts’ in them. The FDA’s acceptable threshold for flour is 75 or less insects fragments per 50 grams of flour. If the mealworm was dead/dried etc I wouldn’t worry so much and I’m not sure what they would do about it, it’s not dangerous to public health
Ah, yeah that’s kind of odd seems like it hatched inside the tin. I would definitely be weirded out too if it was alive . Weird that they didn’t accept the return