This is where you need your team calling you to say you've got someone over your shoulder. And if that's not happening, then it's equally as bad as Justin not just simply looking over it as a cursory look every few seconds.
His positional sense is bad enough at times anyway but what he did today is a droppable offence. I wouldn't expect Ward to help him out because he's so inept too. But Justin should be dealing with it even if there was no-one coming in back post. He's too far out to have let it go out if that's what he was thinking.