The prize will now be considered unclaimed as no one came forward with the winning SuperLotto Plus ticket within 180 days.
The winning ticket for the draw, which took place last November, was sold at an Arco AM/PM convenience store in the Los Angeles suburb of Norwalk.
But the Thursday deadline came and went without a winner presenting the ticket or making an official claim.
Staff at the store say that a woman had recently come in and told them that the ticket had been destroyed when she did her laundry, according to KCAL.
And they even told the TV station they had security footage of the woman purchasing her ticket there.
California Lottery spokeswoman Cathy Johnston said that the woman had not contacted lottery officials, and she was unaware if she had filed an official claim with a district office.
“If she did, we will investigate as we always do. If she did not, there is nothing to investigate and no more we can do,” said Ms Johnston.
And she confirmed that the store’s security footage would not be evidence enough that the woman had bought the winning ticket.
She also urged players to sign their ticket and take a photograph to prove they once had possession of it.
Now the $19.7m cash value of the prize will be given to California’s public schools.
The store itself will also get a $130,000 bonus as its prize for selling the winning ticket.