I lost one this year, Indian Giver. It was new to the garden last year, and luckily cheap to replace. I can't say what happened to it though, as we had a very mild winter and all other named and unnamed DL are doing great. It had done well throughout the summer and into fall; no signs that it was going to kick the bucket.
Becky, how sad for you to lose that one. It was a beauty! Did you manage to get any seeds from it? This would be the only consolation that I could think of
DND, sure would hate to lose one as nice as TOI, especially when I read your reports in the database about how much you loved that one in particular...bet there are ten others that you'd have given up in its place!