Estee Lauder Refused to Refund My Unused Foundation

I recently purchased a foundation from the Estee Lauder Online store and attempted to return it unused. However, customer service informed me that the product couldn't be returned because it had been "opened," even though I never used it. There's no external packaging on this product, so how can they determine if it's been used or not?
I understand if there was packaging and it was torn, but that's not the case here. Even customer service admitted they're not claiming it's been used. The product may have smeared on the cap during shipping, which is inevitable given the long journey. Are you aware that store employees open product caps before selling them?
When you receive the product, you open it too, right? Doesn't that start the shelf life? Logically, every product bought online, used or unused, should be disposed of and not resold. It needs to be destroyed because the inspection department opens every returned item anyway!