It isn't exactly easy to hide a 12 foot tall person. Our societies are not built for people who are 12 feet tall. But 12 foot tall people could hide and probably would as a means of survival, out in wilderness areas. I wonder if National Geographic has any footage of Nephilim out in "the wild". Maybe that is why they have all of these crazy Bigfoot TV shows, so that people will just blow it off as nonsense. Blurring the lines between make believe and reality. Every society seems to have it's own folklore about some kind of giant. Must be something to it. And the Bible even talks about it.
I would not be surprised if there are DUMBs or top secret military bases that would house a giant if they found one,