OOPS! nevermind.
I remember reading a series of newspapers articles about the Somalia battle that was later the subject of the "Black Hawk Down" movie. I haven't seen the movie so don't know if it covered the communication issue I'm about to mention.
The army had a convoy on the ground trying to reach the crashed Black Hawk helicopter. The navy had a surveillance plane watching. The plane would see that the convoy was heading toward and ambush but they could not talk directly to the convoy (I don't remember if it was because they didn't have radios with the frequency the convoy was on or if there was a rule against it) so had to relay the warning and recommended alternate routes back to their own base.
There that would go up through the chain of command until reaching someone who was able to talk to a counterpart in the army, then down the chain of command in the army and finally to the convoy. By then the alternate routes the plane had found were no longer applicable, and the convoy might have even already reached the ambush.
When they got past that it would just happen again farther along with another ambush.
With that being the case it could be operational inertia. Sonar tech hears something weird, reports it to his boss. His boss puts in a morning update the next day, he sees about the sub on the news, but he can't just go sending this info off, he runs it up the chain, eventually a person with authority hands it off to the USCG who then passes it back down, and eventually someone in media gets ahold of it, or someone in an official capacity makes an announcement.