I’ve always assumed that if you lost something on an airplane, it was gone. It’s not like leaving your wallet in a taxi that you can call a few hours later and possibly recover it. Nope, once you walk out of that airplane, your left-behind goods are already on their way to some exotic location without you.
Some airlines, however, are doing what they can to help reunite you with lost goods. Korean Air, for example, has a Lost and Find section on their website. Simply put in the airport you arrived at and up pops a handful of goods left behind, ranging from handkerchiefs, to cell phones and glasses. Or you can search by categories of lost items. It seems that books and glasses are the most commonly left behind.
Many of the items have been thoughtfully photographed and for a small fee can be mailed back to their rightful owners. I’m not sure how one proves they are the rightful owner of a book or iPod, but you do have to present identification to get the item back. If you were never on a Korean Air flight, I doubt they will turn the goods over.