(USDA developed two table grape varieties, secured patents on them, and licensed them to defendant; grape varieties released to growers in mid-2005 and patents secured in early 2006; before the official release a couple of growers began growing grapes from the patented varieties, but did not sell any grapes commercially or give away any mature fruit; defendant had no reason to believe that growers had unauthorized possession of grapes; patents challenged as invalid due to public use more than a year before date of patent application; patents upheld as valid because growers' use and cultivation of subject varieties was limited in scope and private and vines "hiding in plain sight" such that "invention" not "accessible to the public" or "commercially exploited for more than one year before the inventor sought patent protection).