True. But as soon as I thought of the circle, I said to myself 'ah, the idea that it's a straight line is exactly the sort of assumption that you gets you into trouble!' so I threw the whole solution out.

I figured a straight line would be equivalent to a random arrangement with each of the boxes being numbered, so I assumed the vagueness was designed to lead one into making a foolish assumption about their ordinal presentation. Maybe I'm paranoid :-)