It’s not merely a NICS database check, but rather an ATF trace, which is handled in a much less rushed fashion through the ATF National Tracing Center. They start with the manufacturer, and work their way forward to the purchaser, be it distributor, gun store, or individual, and then contact THEM to determine the next link in the chain. It can days, weeks or months to follow a decade-old gun across a dozen or more transactions. This procedure it used with firearms that have been used in a crime, and determines if at any point the firearm was stolen but not reported, used in a crime, or in the wrong hands.
You've got an actual crime committed, this may be justified; in a case like this, it's bullcrap. And I suspect done for either the "We don't like people carrying guns, legal or not, so we'll make this difficult for him" or "We'll make this so difficult he gives up" reasons.