Why should a user "know" they got a cached page and not that more phones came up for sale? How could you possibly spin this as somehow being the users fault for not "knowing"?
Perhaps because I've had my own odd experiences with online and offline commerce, as well as having read about others' on FatWallet.com, I may tend to see red flags where others don't.
For example, in my experience, online inventory doesn't typically get updated very quickly. So, seeing inventory suddenly show up for a sold-out item as I was rapidly refreshing, I think, might trigger my spidey-sense but perhaps other people might not think this way.
In any case, my comments aren't meant to excuse any poor customer service, or any other issues, on the vendor's end and I hope the author's case is resolved to his satisfaction.