Nobody at the table said so[meaning here]

Question

I read this passage in I heard you paint houses:

The night before my testimonial dinner, Russ and I had a sit-down with Jimmy. We sat at a table at Broadway Eddie's, and Russell Bufalino told Jimmy Hoffa flat-out he should stop running for union president. He told him certain people were very happy with Frank Fitzsimmons, who replaced Jimmy when he went to jail. Nobody at the table said so, but we all knew these certain people were very happy with the big and easy loans they could get out of the Teamsters Pension Fund under the weak-minded Fitz.

I'm not sure what it means here. I have seen 'say so' in dialogues like:

A: Hey You said you were afraid of dogs, right?

B: I didn't say so.

Answer 1

So refers to what follows, just like in your own example it refers to what was said earlier. The sentence could be rewritten in the following way without changing its meaning:

Nobody at the table said that these certain people were very happy with the big and easy loans they could get out of the Teamsters Pension Fund under the weak-minded Fitz, but we all knew it.

Answer 2

"So" in this context has the same meaning as when Captain Picard on Star Trek says, "Make it so,": roughly, thus or, thusly.

Answer 3

"Said so" is something of an idiom, meaning "said it was so". "So", in this case, is used as a pronoun (or an adverb, according to some authorities) meaning roughly "what is specified elsewhere in this conversation".