I just has one of these last week too. It was an international package that did offer tracking to the front door of a business address in the other country. It shows delivered on Sunday. Being a business, I agree with the customer's assessment that there was nobody there to receive it on a Sunday, so something wasn't right about that. I went ahead and shipped a replacement package at my cost and I'm currently waiting to see if it arrives. Overall, less than 1% of my shipments fall into this category, so I'm not terribly concerned when I have to resend something as it is made up in the profits of all the successfully delivered packages.
I had another one in December that was domestic US shipping that took three weeks to arrive. My replacement shipping arrived the same day as the delayed one. The customer paid me for the replacement since he had received both, eventually. We figure it got caught up in the Christmas shipping with high volumes.