Police in Hampton Township, Mich., were digging for Jimmy Hoffa yesterday. An informant who's been right before said Hoffa (or maybe parts of him) was under an above-ground swimming pool in some suburban back yard near Bay City, 100 miles from where he was last seen.

After six hours the diggers came up empty. But suppose they'd found him? Do we really want that?

Obviously the family of the long-missing-and-presumed-dead Teamsters union president would like to know what happened to him, as would several generations of detectives and a good portion of the FBI. After all, you're not supposed to get away with the act of disappearing people, and Hoffa hasn't been seen since July 30, 1975, when some party or parties unknown apparently made him an offer he couldn't refuse.

He probably wasn't worried about his safety. True, he'd served prison time for jury tampering and was closer to the mob than scungilli to marinara sauce. But he insisted he wasn't a crook, and he'd been officially pardoned by Richard Nixon, who as we know wasn't a crook either.

So why should he worry about leaving a parking lot near Detroit for a meeting with two guys named Anthony Provenzano and Anthony Giacalone, who may or may not have been a couple of wiseguys? He probably wasn't even wearing his Saint Anthony medal.

The point is that some things in life, like the whereabouts of Jimmy Hoffa and the existence of the Loch Ness Monster, just to name two, should remain a mystery. We need them floating around out there in our imagination, to provide evidence of the uncertainty of life, not to mention material for Jay Leno.

Obviously we want to find Saddam Hussein and Osama bin Laden and those weapons of mass destruction in Iraq. But Jimmy Hoffa is different. Isn't it better imagining him entombed and/or dispersed beneath the end zone of Giants Stadium in the Meadowlands of New Jersey?

And he's not the only one. What if they found "D.B. Cooper," the extremely well-mannered skyjacker who purloined a Boeing 727 on Thanksgiving Eve, 1971, and parachuted into history with $200,000 somewhere over Washington state? True, he accelerated an epidemic of skyjackings, but he never really hurt anybody. Isn't a part of our imagination out there with him, still running free?

Myths are useful, cultural-anthropology-wise, and the most enduring is the unexplained disappearance. This is followed closely by the unexplained appearance, as in Elvis, the Virgin Mary and various extremely undocumented aliens in Roswell, N.M.

We need the idea that not everything in life is nailed down and explainable. The further we peer into the cosmos, the more we figure out the human genome and start cloning in the barnyard, the more popular religions become. We don't want DNA explaining everything. We want some mysteries to be eternal. We want Jimmy Hoffa where we can't find him.

Part of this, of course, is that Hoffa was not always the most savory of characters. He curled his lip at Senate committees investigating the Teamsters and at just about anybody investigating him. We thought he might end up like Joey Gallo, splattered all over Umberto's Clam House, but it was somehow better that he just sort of vanished, like Judge Crater, Amelia Earhart and those Navy aviators in the Bermuda Triangle during World War II.

Occasionally mariners still find boats adrift in the oceans of the world with no one aboard. Sometimes there's food on the table and no sign of disturbance. Sometimes all the life rafts are still on board. The most famous was the sailing ship Mary Celeste, found abandoned in the Atlantic in 1872 en route from New York to Genoa, Italy. The captain, his wife and daughter and a crew of eight had simply disappeared.

Planes go missing all the time. Sometimes they're found (usually during hunting season when the trees are bare), sometimes not. But those missing pilots, like the faces on milk cartons, remain human beings, not archetypal mysteries. They never become legendary will-o'-the-wisps like Zorro and the Flying Dutchman and your high school girlfriend who didn't come to the 20-year reunion but someone said was last seen in Marrakech.

Jimmy Hoffa may be more famous missing than he ever was alive, and he may serve a deeper, more primal purpose. We cling to the unknowable, even when it hovers near an above-ground pool in a back yard near Bay City, Mich.

The vanished Teamsters boss is still in parts unknown.Jimmy Hoffa, left, with Anthony Provenzano in New Jersey before he disappeared; now he's everywhere in the popular imagination. But he doesn't seem to be under that swimming pool in Hampton Township.