Well, I picked up a pal from Gatwick last summer.
After I dropped her home, she phoned me ... she'd opened "her" suitcase, and it wasn't hers!
We had to take it back to the airport. Her case was still there, and the owners of the other case were long gone, having reported their case "lost by the airline". They then had to come back and retrieve their own case.
That made me wonder. The statistics suggest that airlines lose a ridiculously high percentage of passenger luggage. But how much is just stolen by other passengers?
It's low risk theft, isn't it. You nick someone else's case. If you get stopped, you say ... "No, this is mine. Look, it's got my baggage tag right here ... OH GOSH, I am SO sorry! ... This IS your case, after all. My apologies."
I bet that happens, all the time, and the airlines get the blame.