I understood your question. I knew that FEDEX requires the contact phone number. I wasn't sure about USPS but I was pretty sure that if a phone number wasn't listed in the "phone book, i.e. land line, i.e. with 911" with the government , they would not leave the package. Tracking is everything these days with the shipping companies and the USPS, i.e. government.
I have it in my policies that a phone number is required for shipping with FEDEX. I still have to convo the buyer if they don't give it when they buy. FEDEX will not deliver at all without a number. It is good to know about USPS. I had heard that they had cracked down.
Professionalism in business and shipping is very important.
Hang in there, I understand your frustration.