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.