User blog comment:IamJakuhoRaikoben/Chapter 384: Attack of the Stars, Review./@comment-3424593-20140516074407/@comment-1359322-20140517022214

I don't see any reason to be bothered by that, it's not like Lucy has all 12 Keys plus this might not be the last time the CSK will be summoned to battle, so a few more keys might be destroyed in the process again.

Sum it up i don't really care or feel bothered about one key destroyed, as long as it served for a better plot, i'm all fine.