Obviously, you can't put a bike in a carryon, but you can and should pack most valuables in luggage that travels with you, or better yet, keep expensive items on your person. Best advice: leave all good stuff at home, so you won't wind up leaving a message on an airport online "lost" site, like this recent plea about a missing bracelet:
"The value is about £225,000 [approximately $360,000], but the emotional value is far greater. If by chance it was handed in, please contact me as soon as possible." --JFK Lost and Found, posted Oct. 25, 2011
I suspect she's still waiting. Note to travelers: never advertise the value of a missing item.
More weird stuff: an acquaintance who works as an aircraft maintenance technician at a sizable airport he prefers not to name says bags of cocaine have been found on planes, as have sex toys (and you thought TSA screeners were the only ones who found these things). The former was reported to the feds; everything else gets turned in to "lost and found." I'm trying to imagine someone asking an airline rep if anyone's found a, uh, well ... you see the dilemma.
I myself once lost an expensive pair of noise-canceling headphones; never got them back. Other flyers are luckier; a regular commuter on Delta once left a paperback on his seat and the following week, the book was handed to him by the flight attendant who merely said, "I marked your place." Nice.
Now if only Ms. Kardashian could find her lost love; but the way those gals travel, who's to say she's not on a flight right now, finding new romance with a special seatmate?