I'm assuming that it was planted by someone else. Sometimes it is just a matter of giving the previous owner a call and asking them what they had planted. Short of that, all the information possible would help identify it. Many varieties have similar leaves and clusters which is why I didn't even hazard a guess. Color when ripe helps some, size of leaf and exact shape and so on. You could bring a few leaves and a cluster or two to a local vineyard near the friend's house. They probably would have an idea.