I'm gonna offer a "behind the counter" perspective on this, and I'm also going to qualify my opinion by stating that I work full time in commissioned sales, as my only job. Quality customer service keep a roof over my head and food on my plate.
You would not believe the amount of people who walk through my doors and "saw it cheaper somewhere else" without any sort of ad or some other form of proof to show for it. Now, in my business, I get a piece of every dollar that every customer passes across the counter to me, so yeah, if someone saw it somewhere else, I'm going to get on the line, call that place up, get their bottom line, and ensure that it's in stock ('cause facts are facts - if it's not in stock, you can't exactly go buy it for the cheaper price). I want that customer, because I need his business.
On the flip side, I've worked behind the service counter (insert any big box retailer here, I've probably worn their shirt/vest/cap). If a customer comes up to me and "saw it cheaper somewhere else", and they don't have some sort of leg to stand on (and no, a receipt is not a leg to stand on), namely an in date ad, then sadly, there really is nothing I can do for you. The mere fact that the first store took you at your word and made the effort to call the other store just demonstrated over the top customer service (a level of which I wouldn't, as a consumer, expect, nor deem necessary at a store like K-Mart).
You validated a UPC and a price on the phone, which the girl on the other end probably typed into the POS to validate the price. Even given that, K-Mart's price match policy does require the product to be in stock at the competitor's store in order to qualify for the price match.
All in all, yeah - this lady's attitude is crap. I won't vouch for that. But in terms of rejecting the transaction? I'd have done it too. I'd have been kinder about it, but the fact remains:
- A receipt from a nearby K-Mart for a different UPC is not a valid basis for a price match.
- You didn't have an ad, so this, coupled with the first point, leaves little more to the service reps perspective than someone saying "I found it cheaper somewhere else".
As for the repercussions of the return, the margin on action figures is...minimal, at best. Toys of any sort are typically a high turn over item. They're not making much on the sale, and even a store hurting as much as K-Mart isn't going to lose their shirt over a return. I'm willing to bet, in fact, that the price match you received at K-Mart #1 dropped the price below cost, based on my own experiences with markups in that department.
I dont know good luck 
