This is why I prefer to pay for firearms purchased over the Internet using USPS money orders.
That said, how the heck did the postal inspectors and the Coast Guard know that Bannon was on a yacht, and exactly where to find the aforementioned yacht in Long Island Sound? Long Island Sound isn't exactly the Pacific Ocean, but it's not exactly a goldfish pond, either.
Depending on the "yacht" it may very well have an
AIS system on board. If not, even small boats these days have an
MMSI programmed into their
VHF Digital Selective Calling radios that will transmit location info when queried.
Even a small "yacht" is likely to have Global Maritime Distress Safety System (GMDSS) gear and SATCOMS aboard, almost all of which have their own GPS chips (or feed from the vessels's GPS) and transmit location information.