Visibility of template specialization of C++ function

Question

Suppose I have fileA.h which declares a class classA with template function SomeFunc(). This function is implemented directly

Answer 1

Brandon: that's what I thought - the specialized function should never be called. Which is true for the second application I mentioned. The first app, however, clearly calls the specialized form even though the specialization is not declared in the header file!

I mainly seek enlightenment here :-) because the first app is a unit test, and it's unfortunate to have a bug that doesn't appear in the test but in the real app...

(PS: I have fixed this specific bug, indeed by declaring the specialization in the header; but what other similar bugs might still be hidden?)