While I wholeheartedly approve of your very forgiving attitude, I can’t help but wonder if actually making a big deal out of it would make them less likely to do it in the future because they would have learned a valuable (and expensive) lesson.

Large companies seem to think copyright laws should be a one way street and it is extremely frustrating when this sort of thing happens. If you had “borrowed” something of theirs and put it on your site, I suspect they would not have so lenient an attitude!