What is the shell company?
I wouldn't ever think that anything called "Facebook XXX" is a facebook app, even more so if it's clearly sold by a shell company. It was hiding, even though it was ironically in plain sight.
For any sane person, the only way to know the "official" ones are to check the developer account, in this case, it was not Facebook.
Hence, for any sane person, the only reasonable assumption was that it was not a Facebook sponsored one.