I don't know what to tell you.
As I said above, I copied and pasted QR Code Reader and Scanner into the iTunes Store search field, then hit Return. What I got was a results page titled "Showing results for 'QR Code Reader and Scanner,'" with a horizontally scrollable list of 32 iPhone apps. The first or leftmost app shown was, in fact, QR Code Reader and Scanner. The app you're referring to—Scan—did appear in the results: it was fourth on the list. (FWIW, the app's actual name appears to be just Scan; the "QR Code and Barcode Reader" is a descriptive phrase, perhaps added by the developer to improve the app's performance in search results. It certainly does make referring to it an unwieldy exercise.)
As for whether the difference between your and my experiences is attributable to the difference in operating systems, I can't say. I did run Mountain Lion for about a year, but, lacking an iOS device, never paid much attention to apps in the iTunes store.
Last edited by dkmarsh; 08/27/14 10:16 AM. Reason: added last paragraph
