There is a phenomenon that has been discussed on other knitting blogs across the net, and even noted by Lily Chin at a last month's Greater St. Louis Knitters' Guild event: it is quite common for designers to come up with very similar designs at nearly the same time.
I talked about this on my July 13 post below relating to the stitch pattern used in the ever popular Monkey Socks.
This morning I woke to find this thread on Ravelry: http://www.ravelry.com/discuss/patterns/323852#reply_form.
If you're not on Ravelry, Krystofer came up with a sock design that he also didn't realize was essentially the same as Monkey socks: http://queerknits.blogspot.com/.
So 'unventing' applies not only to technique, but also to design.