Pull the oil pan drain plug and fish around the bottom of the pan through the hole with a flexible magnet. Chances are you'll get the nut out that way. If the nut is in one of the splash-oiler troughs it can do some damage to a rod dipper the first time the crankshaft turns.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!