Is or can be
Have you been, Jack?
short for
How have you been, Jack?
Is or can be
Have you been, Jack?
short for
How have you been, Jack?
In written text, no: "Have you been" is not a greeting query. It could be used to confirm or ascertain a previous state, although most likely the "been" would be left off:
John has never been to England.
Have you been?
-or, more commonly-
Have you?
The standard greeting is, as you say, "How have you been?" In spoken discourse, however, it's very common to contract "How have" to "How've", and in some accents or in rapid, under-enunciated speech, it's quite possible to lose some or even all of the rounding on the ow sound, so the word comes out sounding closer to "have" than "how've".