I'm guessing this is more likely memory lapse than serendipity. I did start some of these from seed that GB gave me but I have no recollection of planting this in the front garden. But, since it's the identical one that I was oohing and ahhing over at her house last year, I'm assuming that's exactly what it is.
Either way, I love it and I'm planting way more of it next year if I can remember to grab the seeds. Since this one is located in my front garden and I rarely go out to the front garden, I've yet to see any actual butterflies. Next year I'll plant them in the back so that I can see them from my kitchen window and I'll be ready when the butterflies show up!