It would be remarkable if they had found it already. It's a big ocean out there. When the USS Indianapolis was sunk by a Japanese torpedo, the debris in the water were the survivors. They were not spotted for four days.
Uh, we sort of have new imaging resources these days and the potential area based on radar track is fairly small. Plus the water is relatively shallow. It IS very odd.
“the USS Indianapolis “
N0 one was looking for them and their location was unknown. They were on a secret mission to deliver the A bomb. That is why no one knew where they were.
The flight path is known here and they had almost immediate notification that contact was lost.
No one was looking for the Indianapolis.