I call it "Environmental management". Ecological conservation along with appropriate management (ie thining) to propagate well being throughout the biosphere. If done correctly, the original site is left in an uncluttered and vibrant state and secondary sites benefit greatly from the increased diversity. It is very much a "Win - Win" situation.
Greg is right there are quite a few I probably wouldn't notice missing ,but that one would be a problem it is planted all by itself and I have plans for it and I will be be installing alarms on the bulbs when you 2 come by in the spring.
Who said anything about the Spring? Winter kill off is a term you should come to terms with. Now, explaining why the rhizome disintegrates (ie disappears) is a much harder proposition to tackle.
The Monterey Bay Iris Society (MBIS) hasn't posted Joe Ghio's 2014 introductions yet, but they've posted their Feb. newsletter which has a few pictured -- gorgeous!