Good question. The Japanese thought they sank her at Coral Sea. They had a lot on their plate at Midway. They might not have had time to figure out which ships on our side got sunk. If any of their subs had hung around after the battle they probably knew a carrier had gone down, but maybe not which carrier.
The Documentary Channel recently broadcast an excellent show titled, “Tin Can Sailors Will Not Be Forgotten.”
It deals with the reunion of sailors from the destroyer, USS Morris. I believe that was the Morris in the picture next to the Yorktown. Those sailors who made it to the reunion spoke about that particular incident and how they witnessed its sinking.
It’s questionable how much the Japanese believed the after-action reports of their pilots. The Japanese pilots started the war with inflated claims, but as the war went on their claims went from inflated to the realm of fantasy. Even though all nations suffered from exaggeration of damage inflicted on the enemy, and it extended to submarine skippers as well as pilots, you wonder whether they really believed the reports.
But as things stand, the Japanese probably know that the Americans are as short of aircraft carriers as they are. But on the other hand, the Japanese also know that we are building at least ten Essex-class carriers (it’s actually more, but they will have to find that out the hard way). They also know that they only have ONE fleet carrier under construction, Taiho, and she won’t be delivered to the fleet until 1944.
That was the real folly of their Midway operation. The only strategic military asset the Japanese had was Kido Butai; the concentration of six flattops capable of fighting as a coordinated strike force. They also knew that it was a wasting asset; their strategic advantage was not going to last forever once all those Essex class carriers entered service. They also should have known that if they lost that strategic asset in combat, their advantage was gone and they would never, ever regain it.