Blue Eyed Grass, Sisyrinchium angustifolium, isn't a grass at all, rather a primitive Iris. It's easy to grow, as long as you give it full sun and enough moisture in good draining soil. In your zone, it'll spread like crazy, and will likely be evergreen.

donn is right blue-eyed grass is a member of the iris family, a sisyrinchium. However there are a number of different sisyrinchium species, including a "yellow " blue-eyed grass that is an excellent pond plant tolerating moist and boggy conditions. Sisyrinchium angustifolia would be lovely in a rock garden and hardy to zone 3.

I like this plant. Had a volunteer growing close to the part of the roof where water ran off (but shouldn't). I guess the gutters were a little malfunctional. Then one day it disappeared. The area was well draining just because of all that rain that would gush out. I wonder if I'll ever get another volunteer?

The actual plant itself is fairly short-lived (couple seasons perhaps) but if it went to seed you may find some babies especially if it liked it's original spot before you had the gutter malfunction.

Sisyrinchium angustifolium...this is a cool plant. I found a selection of it, 'Lucerne', offered at several online retail nurseries (if you can tell the varieties apart):

http://www.plantdelights.com/Catalog/Current/Detail/04782.html

http://www.santarosagardens.com/Sisyrinchium-angustifolium-Lucerne-p/sis-luc.htm

http://www.highcountrygardens.com/catalog/product/91850/

Like gonativegal said, the original plant may be short lived, but it'll seed and create a long lasting stand. Not surprised where it found a home, does well in those kind of moist conditions. I hope some emerge for you!