I've got a message from a friend which is an English native speaker from Africa and he he wrote me "Are you back?" in meaning of "Did you come back?" (to the country that he is in). This is the first time that I came across such usage and I would like to ask if it is correct usage in English or just slang or something like that?
Are you back? is current BrE and quite appropriate to ask of a colleague who has been away and might or might not have returned.
Did you come back? is a grammatically correct question but for different circumstances, such as if you had said "I just went to the most wonderful place on Earth".