Do you mean were not allowed to return by the Japanese? Or that they were held as prisoners of war by the US?
The Japanese Admiralty was so afraid that any reports of the sinking of their carriers at Midway would hurt national morale so much they ordered that the survivors never be allowed to return to Japan. They were kept in hospitals outside the country and those who were well enough were eventually put on ships that would never make port in Japan.
Saw a History Channel show about the battle. A Japanese military reporter was on one of the carriers. After the battle he was sent back to Japan but not allowed to leave the base for a year. He was under strict orders never to talk about or write anything about the battle.