I think the comment by @MasonWheeler on the selected answer kinda explains it best. The girl is the guy's wife. If she said "Hey Honey, I'm going to be at work all day" or "I'm going to xyz's house for the night" the husband would know where to go.
The assumption that this question hinges on is that the husband has no idea where his wife is. You can't answer the riddle if that changes, and this wasn't addressed. It would, honestly, be less likely that the husband didn't know (you probably know where at least most if not all of your household are right now, yes?)
In regards to the closing reason, it addresses that; The question is posed such that there are assumptions necessary to answer it. You want to ask the questions in such a way that when the answer is revealed, everyone goes 'Oh yeah that's the one true answer.' The answer in this case still depends on information that isn't included in the question that isn't guaranteed to be true in general.
Even if that was resolved, to me (i.e. this part is more an opinion of mine, and less important than the above) this is more of a 'Gotcha!' sort of trick than a puzzle requiring alternative interpretations or problem-solving. It verges on a punchline of a joke more than the answer to a problem to be solved.
The second part is up for debate, I'll agree, but I think the first part really makes a concrete case.