Wow, you're absolutely right. I downloaded it one time when I set up my 6 Plus, and then deleted it. Also can't find it in the App Store anymore. What gives? Going to try the same for the other apps we got the the new phones.
I think Apple feels that since they made the editing feature in the regular photos app (the old camera roll area) more 'robust' that it eliminates the need for iPhoto which if it's true I hate that.
I was really excited to try iPhoto on the 6 plus screen.