Most likely you heard the surname mentioned once or twice and forgot it, but your subconscious remembered it.
Lightsleeper, what is it about this dream that makes you think it is definitely a good dream, even before you know about the colours of the cars, which you think is significant. How can you tell if the dream is good or bad before you know the truth about part of the dream you think is important.
You might find this information on hot and cold reading to be interesting.
http://meaningofdreams.org/phpbb2/vi...hp?p=5440#5440