So, i finally watched the non-blip version of that (couldn't be bothered to look it up before)
Umm, correct me if i'm wrong, but they were walking in from a grassy, open (and SUNNY) area...into what would look like (from their perspective) into a very dark bushy area. They would not have been able to see through that bush until they got out of the bright open area...just about where you shot them is where they might have finally might have been able to see you. Not really the case you make it seem in your description...i wouldn't call that "hiding in plain sight."
In this particular situation, it is likely you could have been wearing more or less anything, including a clown suit, and b/c of the physics of them walking into 'dark' wooded area from a very bright clear area, they would not have been able to see diddly squat. I personally avoid going from very light areas into a bushy dark area for this very reason, you can't see JACK until you are past the first bush (which they weren't).
I like Keeblers reference to the "just don't be the wounded Gazelle" theory. So True.
But when ever i question just how much someone could have seen when i ambush them, i go back with someone (usually my brother) and reenact the circumstances. Here are some examples of me going back and looking at what could be seen from the other side. (in this one, it was my bro who ambushed me, then called out b/c he though i could see him after his hopper fell off)
Here is the link to the facebook album and description of the event. Just click "next" to see the other pics of the incident. This also shows that it is always easier to look out from a shaded area than into one. Jeremy Nickoson's Photos | Facebook