Officials at the Department of the Interior scrambled this week when their annual tally of the nation's rivers repeatedly came up one short. 'Okay, let's start againwe have the Ohio, and then there's the Mississippi, the Missouri...' said frantic Deputy Secretary David J. Hayes shuffling through a clutter of maps on his desk. 'Wait, a river's the one that flows toward the ocean, right? Or is that a tributary? Jesus, are rivers and tributaries the same thing?' Until the missing river turns up, DOI officials are advising all citizens to remain vigilant and immediately phone the department's National River Hotline should they encounter any unusual bodies of water. 