I am not 100% proficient in the way Big Lots handles merchandise (I only ever stepped foot in two of them when searching for these damn molded singles!) but they could have just held a temporary stock.
As far as I know, it was the only place in the USA with these toys outside of ridiculously overpriced online retailers.
Lets just hope Hasbro has plans to release more in the future or something!
*Update* Looks like Meijer still has them! Sadly that's not a very common store here!