Er - what? No, 18,000 isn’t a sample size. 18,000 is the total stolen/lost gathered by the ATF.
I was comparing it to the number of owners, which is ~80million (granted an owner more than likely got more than one gun stolen, and possibly more than one lost, so the 9,113 lost isn’t the necessarily the number of people).
I guess if you wanted to compare sample size, the 18,394 is the number reported lost or stolen is out of the estimated 390 million in the US.