In the mean time, I ran across a few other related articles, including this one from the New York Times, published in 2002:
At Seattle-Tacoma International Airport, 330 laptops were left behind between September and April, up sharply from only 7 in the comparable period a year earlier...in the last three months, the airport collected 204 misplaced laptops. In Denver, airport officials resorted to posting signs at security checkpoints saying, ''Got laptop?'' after 95 computers were left in February alone...
...The efforts to find laptop owners have largely paid off. In Denver, for instance, all but 20 of the 600 or so laptops left behind since September have been reunited with their owners...
...At other major airports, including those in Boston, Chicago and New York, officials say the problem of misplaced laptops has barely registered...
That obviously doesn't jive with the Dell study. If you figure a large airports were finding at most a few laptops per day in the months just after 9/11, either the study is way off, or the laptop loss problem has gotten an order of magnitude worse since then.
The lesson Dell wanted us to hear? Buy our security software.
The lesson we all heard? There is an epidemic of lost laptops.
Me? I’m still trying to figure out where they pile all those lost laptops (unless, of course, the study is bogus).
 Airport Insecurity: The Case of Missing & Lost Laptops, Dell
 At Airport X-Ray Machines, a Mountain of Forgotten Laptops, Jeffery Selingo, New York Times
 Data doesn't add up on study of missing laptops at U.S. airports Agam Shah, Computerworld
 Who really believes that fliers lose 12,000 laptops a week?Sean O'Neill, Newsweek
 The Airport Notebook Revolving Door, Robert Richardson, CSI
 Hundreds of Thousands of Laptops Lost at U.S. Airports Annually, Bruce Schneier.
U.S. Travelers Lose 12,000 Laptops Every Week Elaine Chow, Gizmodo