Package says delivered, but I didn't receive it?

I have an order that was said to have been delivered yesterday. I did not receive this package. My mail comes to a large set of locked mailboxes that is used by everyone in my neighborhood – everyone has a key to their own private box. When I get packages, the mailman puts a key to a large ‘package box’ in MY box so the package can be delivered to me securely. I did not receive said key, so also I did not receive the package.

I contacted my post office. They confirmed what I knew – that it shows ‘delivered’ – and said it’s out of their hands. If someone in my neighborhood received it, they’re certainly not willing to admit to it. The post office rep said I needed to contact you (HSN) directly. What the heck do I do now?

Thank you!