No, that's not what happened. I'm guessing you saw this news before under a clickbait title.
It's not about where gold was found, it's about where he stashed it later. These are assets that are (or were) in his hands which partially belong to all the investors he defrauded.
I remember once reading two bits of news about people given similar sentences. One for copyright infringement, the other for sexual assault of a teenager.
The ongoing refusal to answer questions under oath is.
He could have agreed to talk anytime and been released shortly.
It's a civil proceeding not a criminal proceeding so he would not be incriminating himself.
He could argue that by answering he would be admitting crimes and opening himself to criminal liability. But there's a possibly they give him immunity and that route is taken away.
“On my life, I will not part with a single coin.”