Just because a person has never seen something doesn't mean that it does not exist. I once found a piece of 'lightning glass' and I never knew it existed.
This link gives the names and countries of companies selling dried butter beans as well as many other types of dry beans. Yes, Dried butter beans do exist.
http://www.21food.com/product/...
Dinu, The beans look similar to ones sold as "Heirloom Christmas Beans"; the color pattern can vary.
Edited to add link with photo:
http://www.americanseedco.com/...
This is the image of the Christmas Lima Beans on the American Seed Co website:
