Melodica- Good for you on blowing the whistle, I'd do it again in regards to the bettas being hidden. My Walmart used to sell all kinds of freshwater fish, but after a number of complaints they stopped. Is this nationwide?
Anyway, they still carry bettas, but I refuse to buy them. Poor little buggers sitting in an inch of water in a cup- it's heart-breaking but I don't want to perpetuate the cycle. I buy my filter packs from Walmart because they are (significantly) cheaper, but that's about it.
My local pet store keeps them in small bowls, but they look immeasurably healthier. I think that someone at least changes the water. My male and three of my sorority girls were purchased there, and all are healthy and fine.
I'm surprised there was even an employee around; I can never find one.