User blog comment:IamJakuhoRaikoben/Chapter 394: Juvia vs. Keith, Review./@comment-5873677-20140725134148/@comment-7418318-20140725160433

I know, but we never learned under which circumstance F-Rogue killed Sting, so maybe it was a contributing factor to his madness rather than the result.

And since we heard that Frosch might die, setting him up as the "obvious" victim and then switching over to someone else would make a good surprise.

I'm sure in this timeline Frosch's death will be prevented some way or the other by Natsu who will then sprout some Nakama speech along with the line "I won't let you become like that bastard from the future" or somesuch.