Hi Sissy, I was just going to give you the benefit of my knowledge of Iris but it seems I'm too late to save the day which I'm sorry about. Its hard to say from here what killed your plant, someone did mention Iris Borer of which the variety you have is susceptible, details of this pest can be found at http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/e122irisborer.html if you're still interested. Iris do like well drained soil in a sunny position although I believe they will tolerate some light shade. Don't give them fresh manure as this can cause rotting of the rhizomes. Bob.
I'm sorry that it seems gone. It still may come back next year. I saw these for the first time at L0wes yesterday and thought of you. I'm hoping they mark them done just a bit more knowing that you had trouble with them. I hope you guys have a great time at the lake!
I would love to hear from you and if you can leave a comment, I will visit your blog, too!