The U.S. Post Office offers a service called "Informed Delivery" where they send an email containing images of first class mail that is due to be delivered later that day. So when my "Informed Delivery" showed a mail piece coming via Royal Mail, I was thinking it was the Mastercard. But no, everything else was delivered but that.
I waited another week and half, hoping the card was delivered to a neighbor by mistake and they would put it in my box, but no luck. So I finally had Goldmoney support cancel the card and applied for another one.
A Mastercard arrived in the mail not long after that, and I assumed it was the new one. But actually it was the old one. This was now four weeks after the Post Office said I would receive the original card.
Whether the card was on my neighbor's desk in a pile of junk mail, or kicking around the local post office someplace, I don't know. Things were very confused for a while between the two cards, but Goldmoney Customer Service quickly straightened everything out for me. Thanks!