Yeah look at it from the bright side. Next time don't try to think about topics to talk about, just let conversations flow naturally, hop in with whatever they come up with and build confidence. It is not an interview you're supposed to be relaxed.
Besides this the only thing you ruined on that roadtrip is your own image of yourself. Don't let SA fool you it is your mind (that little devil) that convinces you you performed badly. Reality will show you you did well, you'll see.