Yeah, I can't rule out some more elaborate con but at least from the story as it's told here, it sounds like all of these folks were in a hurry, the author wasn't paying attention and didn't make sure he had his laptop before moving on, TSA handed it to the wrong person, and that person thought "ooh, score!"

Or maybe she didn't realize for a while and by that point, a combination of laziness and desire to keep this shiny, luxury model computer that had accidentally ended up in her possession led her to just hold onto it.

I think the number of people who will decide to keep something they find (dropped wallet, misplaced laptop, etc) is much higher than the number who would actively go out of their way to steal something. The end result is the same but I think psychologically, it takes effort to go out and steal whereas it takes effort to track down an owner while keeping a found item just requires apathy and/or greed.