The private diary was sold for $40,000, at the same time that Joe Biden was running for president ahead of the 2020 election.
According to Justice Department court documents, the two people first tried to sell the diary to then-President Donald Trump's campaign.
Then they turned to a conservative activist group.
The group has been identified as Project Veritas, and it offered the two people $20,000 each for the diary.
The group also allegedly encouraged the people to steal more items.
Project Veritas never published the diary, but the conservative website National File did.
The two people risk up to five years in prison.