A Japanese ship was en route in the open sea

A Japanese ship was en route in the open sea. The Japanese captain went for a shower removing his diamond ring and Rolex watch on the table. When he returned, his valuables were missing.
The Captain immediately called five suspected crew members and asked each one where and what he was doing for the last 15 minutes.
The Phillipino cook (in a heavy overcoat): I was in fridge room getting meat for cooking.
The Indian Engineer (with a torch in hand): I was working on generator engine.
The Sri Lankan seaman: I was on the mast correcting the flag which was upside down by mistake.
The British Radio officer: I was messaging to company that we are reaching next port in 72 hrs from now, that is Wednesday morning at 1000 hrs.
The British navigation officer: I am on night watch, so I was sleeping in my cabin.

The captain caught the liar. So who is the thief?

Click here for Answer

The Sri Lankan Seaman : because the Japanese flag is the same, even upside down!