It happened to me only once in my life when I worked as a flight attendant. I still remember that it was a Frankfurt flight. After the flight when all the passengers disembarked the aircraft, I found my bag missing. I reported to my supervisor and other colleagues and one of them said she kind of saw a passenger carrying something similar with a crew bag when she left the aircraft. However, she was not sure if it was a real crew bag so she just let her go. I was so shocked because I had my passport, other IDs, cash, and everything there in my bag. I was rushing to catch the passenger but I was stopped by my supervisor because I was not allowed to leave the aircraft without permission of the authorities. But my supervisor contacted ground staff to find the thief. You know what funny thing is? The thief was a wheelchair user which means she was being assisted by the ground staff at all times and she was not able to even run away when it was discovered. The wheelchair passenger was caught very soon and my bag finally returned to me. Luckily nothing was missing.