A Japanese ship was making its way through the Arabian sea. The captain felt like taking a bath and thus went to bathroom after removing his Rolex watch, gold bracelet and keys to his new Bugatti Chiron...
When he returned back from the bathroom, he found out that his valuables were missing.
He suspected five of his crew members, so he called them in and asked all of them what were they doing in for the last 15 minutes. They replied as follows:
The French cook (with a butcher knife in hand): Monsieur, I was in the cold room, getting meat for cooking.
The Indian engineer (with some tools in hand): I was working on the generator engine.
The Bangladeshi seaman (empty handed): I was on the mast correcting the flag as it was upside down.
The American radio officer (carrying Beats headphones): I was messaging that we will reach to port in next two days -- Friday morning, that is -- around 1143 hours.
The German navigation officer (empty handed): I was taking a nap before my night watch.
Upon hearing all of their explanations, the captain determined who stole his belongings.
Who was the thief, and how did the captain know?
source: A puzzling contest, named Operaomnia, in my college.