Hi!

A report from one side sinking a ship/submarine from the other side does not automatically mean that it really happened.

There are several reasons why there are dozens, if not hundreds of reports like this in WW2 (including the European Theater of War):
misinterpreted bubbles on the surface, releasing of some oil from the sub to make the chaser think the sub is sunk or whatever.

I have not checked all sources of Japanese submarine losses but I hope you have.
So if no loss is reported for that date then I guess that one of the above mentioned incidents happened.
And three weeks after the 'Day of Infamy' (attack on Pearl Harbor) for me it is not hard to understand that a report of a whatever small victory it was (and therefore highly appreciated and accepted without further investigation) lead to a decoration at once.
And this without a sense of betraying or something like that but just to boost morale within the public and within the troops and in a spirit of thinking that it really happened.

--

Best regards
Thorsten Reich

www.Forum-Marinearchiv.de
www.Historisches-Marinearchiv.de