No one can track down Joseph Mifsud, a professor who reportedly met with George Papadopoulos, a former Trump campaign adviser, during the 2016 US presidential campaign.

Mifsud allegedly told Papadopoulos that Russia had "dirt" on then-Democratic presidential nominee Hillary Clinton.

Mifsud's finacé told Buzzfeed News that he cut off communication with her when his name leaked to the press last October.

A professor who allegedly told an adviser for Donald Trump's presidential campaign that Russia had compromising information on Hillary Clinton has gone off the grid, and even his Ukrainian fiancé hasn't been able to reach him.

Earlier this week, Buzzfeed News reported on the mysterious case of Joseph Mifsud, the university professor and foreign policy expert who reportedly acted as a conduit between Trump campaign staff and the Russian government during the 2016 US election.

Last October, Mifsud was referred to — though not by name — in a US court document, which confirmed that former Trump adviser George Papadopoulos had met with him while living in London.

The document said Papadopoulos told FBI agents about meetings with Mifsud, during which he was made aware of "dirt" on Clinton, then Trump's rival for the US presidency.

But since his name was revealed in the press, Mifsud has gone silent. His bio was removed from a university in Scotland and another institution in Italy where he previously taught. They now show '404 Not Found' error pages.

In WhatsApp messages revealed by Buzzfeed between Mifsud and his fiancé, Anna — who spoke to Buzzfeed on the condition that she be referred to only by her first name — the professor urged her to not speak to journalists.

"Someone from London [sic] journalist asks about you," Anna messaged Mifsud last October 31.

"Do not reply please," Mifsud messaged back.

That was the last time the two have been in touch. Anna has since given birth to a baby girl. She says Mifsud is the father, according to Buzzfeed.

Italian prosecutors are also having a difficult time getting in touch with Mifsud. They have been trying to notify him that he is being summoned to appear at a court hearing in July in response to allegations of financial wrongdoing, but the records at the prosecutor's office in the south of Italy say Mifsud has been "unreachable," per Buzzfeed.

Mifsud is accused of inflating salaries for certain professors at universities in Sicily, where he used to work.

Anna claims that Mifsud, a Maltese national, has connections to high-ranking officials in the Russian government, including the Kremlin's foreign minister, Sergey Lavrov.

"He said, 'I have dinner with Lavrov tonight. Lavrov is my friend. Lavrov this, Lavrov that,'" Anna told Buzzfeed. "He even show me picture with Lavrov."

Despite the claim, there is no evidence as of yet proving Mifsud and Lavrov ever met, or that the former professor has any ties to the Russian government.

But according to an interview published last year by the Italian newspaper, La Repubblica, Mifsud admitted that he was the unnamed professor in the US court document about Papadopoulos. He also denied any wrongdoing.