As a "devil's advocate," (no fun), I will say something as a retailer, albeit in the vitamins/beauty product world. We are constantly missing hundreds, yes hundreds of our items at a time--so many I can't even keep track. I know that it's worse than it was 5 or 10 years ago, but even then it was a problem.
Customers are mad, and when I explain to them and even show them with our technology that yes, the computer automatically orders this thing every week--sometimes they are okay, and sometimes they want to do a sit-in.
I would guess this applies to clothes, electronics, any product. With a very few exceptions, we do not get information about why something is out of stock, and at this point it's unreasonable to try and find out--too many things missing. A consumer can just as easily call the supplier--and they probably won't get an answer, either.
People sometimes seem to be a bit out of touch with supply issues. They get mad they can't get something online from Amazon, yet they think somehow we're going to have it. If you try one or two places and can't get something, good chance is the product itself is in short supply, not the retailer.
I would guess an entity as big as Nordstom also has an automatic ordering system, and that they just couldn't get this thing--whether there's an issue with the plant that makes it, or the material, or whatever.
We had a huge promotion on quercetin for three months, with displays everywhere. Yet for half that time, we could not get the product. We weren't making a stupid choice or flaking out....there was none to be had. And I wish people would understand that. When you're talking about a product, you're talking about many many stages involved in making it, and there could be a factory fire in Thailand. Not a "no good" vitamins manager who can't get her shit together to order the thing you need.