Well, after agonizing over this, I went back to the shop and explained the situation about the mold. The guy swapped them out without so much as a blink. I got 3000s instead of 2000s from a different box.
He took the ones I brought back, though, and put them right back in the box I got them from, mold and all.
The shop is less than a mile from my house, which is nice, but I see I'll have to look closely at everything I buy.

Thanks again,
Matt