Sephora Denied me a full refund for items returned; claimed I returned only certain items instead of all the items listed on return receipt. San Francisco CA

I ordered 20 items on 4/18 from Sephora, totaling $451. I received them on 4/22. I kept 5 out of the 20 items and, on 4/23, I returned 15 items. I did not take a picture of the items I returned; I simply placed them all in ONE box and sent them back (with the return slip inside the box) via USPS, as per Sephora’s instructions.

It is now 5/12, and after several phone calls with Sephora Customer Service, I am being told that only 4 of the 15 items were actually received in the box I sent and that those are the only items for which I will be receiving a refund. Customer Service Rep told me that in order to have proof I actually placed all 15 items in the box, I should have taken a photo of all the items. I have never heard of such ridiculous demand. Why is that not written as part of Sephora's instructions? 

I have tried to elevate this issue to the supervisory and managerial level at Sephora but I was basically told that since there is no photographic proof on my part that I actually placed all 15 items in the box, it is their word against mine that I did not return all the items that I listed on the return slip. So, I am now out over $350 for items I did not even keep! And, for all I know, it was most likely people at the distribution center who "lifted" the items out of my box. I also have no photographic proof that the 11 "missing" items were not actually there. When I requested a photo from them, they told me it'd be impossible and that the people at the distribution center "are never wrong" -- and that's a direct quote. 

I am at a loss (quite literally). I honestly never thought to take a photo of the items. And, had this not happened during a pandemic, I probably would have returned the items at my local Sephora store instead of shipping them back. However, due to Covid-19, I thought it'd be safer to send the return back via mail. But now I'm being penalized. It is degrading and humiliating to be treated as a liar and a thief; I have never been treated like this as a repeat customer in good standing. 

Will never shop at Sephora again. Though I still hope to receive my refund!