In practicing for the upcoming Operation Husky scenario (Ju 88's with torpedoes going after CV's and cruisers), I found that there are instances where a torpedo hit will be seen by the pilot but not seen by a person on the CV.
I could see hits on the CV if an object (like a gun) got destroyed in the hit. But if the hit didn't destroy any objects, I wouldn't see the explosion, but the pilot would see it.