Got to agree with the previous posts, a litre of oil MIGHT have been ok on a smaller engined car but on a V6... not likely. The sounds your refering to when you pulled up to your mates will be your engine internals, my BMW did the same thing, the car may feel fine after putting the oil back in but come the next service, if it makes it, you may get a shock. Best thing is to get it to the garage straight away.