Big boars are generally pretty sneaky for one. Like that big buck, they don't grow real big by sticking their neck out often.
For myself, I've never seen a monster boar but people I hunt with have. I've jumped a few, spooked a few, but never had a shot on one. In any case, I've always been told a big old gnarly wild boar is about the toughest meat you can get. Our goal was always to take a smallish sow for the quality of meat.