Maybe you can go to the dealer with your friends car and say "why does my car make that noise, but his does not? it does not sound normal to me"
other than that, probably not much you can do; other than wait to see if the other issue shows itself again
make sure they recorded both issues so there will be a history showing that it was there from the start
other than that, probably not much you can do; other than wait to see if the other issue shows itself again
make sure they recorded both issues so there will be a history showing that it was there from the start