I've worked at gun stores for about 4 years now, and I'd estimate that well over half of all customers make some sort of mistake on the 4473. The vast majority of those are corrected on the spot when pointed out by the salesperson, but not always. With the huge number of mistakes made by customers and the amount of paperwork most shops have, it's not surprising that a mistake goes unnoticed once in a while.
And the especially annoying kind of mistakes are ones like the customer misspelling their city of birth and I get dinged for it by the person who checks our paperwork. How the heck am I supposed to know that when the person wrote "Osbourne, Kansas" they were spelling it wrong? I've started Googling cities I don't recognize just to make sure they're spelled correctly on the 4473.
No, this was your mistake. Sure, it would've been nice if they had noticed it when you were in the store and I can understand your frustration at having to drive back there, but ultimately it's your responsibility to spell the name of your own hometown correctly.