If A has already gone home, then ask: "Did A say bye to you?" If A is still around, then ask: "Has A said bye to you yet?" These examples might help: A has already gone home. You: Did A say bye to you? Your friend: Yes, she said bye when she was leaving. A is still in the building. (Maybe A told you she was going to go home soon) You: Has A said bye to you yet? Your friend: No, she's still here. I think she's waiting for a cab.