Tl;dr: they knowingly double-charged me on separate credit cards.
The sales associate swiped one of my credit cards, claimed it was rejected, and then swiped another one of my cards. Then I found two identical and duplicate charges on my cards (one on each card) for one transaction.
I'd like to think the store didn't attempt to maliciously double charge me in hopes I wouldn't notice.
I called the store, they "apologized," said it was a common occurrence (how many shoppers have not noticed they've been overcharged?), and to date they have not rectified their convenient mistake. Each time they say the manager is out and only the manager can approve retroactive changes. How convenient.
This is an easy fix with a call to my credit card companies, but no one should have to go through this trouble for a friggin' hat.