Yes. And this does not even sound like a customs situation at all; this sounds like airport security (i.e. metal detector / x-ray people on the way out of the country to the gates) found a round, called the bomb people, the bomb people were not particularly concerned with it and they threw it in the trash-- and some required paperwork was completed. This seems completely unrelated to customs. That said, who knows where the paperwork went and South Korea SES is a partner with Global Entry; however the OP was not "found in violation of any customs laws" as best as I can tell from what the post reports.