Sure, if there was any question, players could have asked for a ruling. But, that's just it, there wasn't any question in Dustin's mind, and I doubt there would have been any question in most people's minds. I couldn't see any indication that area had been man-made and intended to be a bunker, and CBS went back after the fact and gave us a pretty good view of the area. If it was a bunker, the fans were not only standing in the bunker all day - they were in the bunker with Dustin when he was playing the shot.
Feherty said that he never considered for one second that might have been a bunker. And, he isn't some nervous kid trying to win his first major and, as a possible result, inclined to not be completely aware of what's going on around him. Feherty was the on course reporter. A big part of his job is to get to the ball and size up the situation, and to then tell the viewers anything they might need to know, or anything that might be the least bit interesting (or not), about the situation. He wasn't distracted by thoughts of what he needed to do to win the hole and contemplating a shot decision - his main job was to be aware of what was going on (particularly with lies), and he's been around the block enough to have a pretty good feel for that. If he says that it never occurred to him that sandy patch might be considered a bunker, I tend to give that some weight and think that the same would be true of most of the players. Not that it matters, but it certainly would have been true of me.
The ruling was probably right - that's one of the things about golf, it takes the emotionless (read: even-handed) and context-irrelevant application of the rules pretty seriously. But, allowing the situation to exist to begin with was a mistake - not a mind boggling inept one, but a mistake nonetheless, and one that doesn't reflect well on the PGA's attention to detail.