SAN FRANCISCO—San Francisco Programmer Stefan Thomas has forgotten the password to his Bitcoin account which has more than $220 million in bitcoin currency.

Thomas has a small hard drive called an IronKey that holds keys to a digital wallet that contains 7,002 Bitcoin, which currently totals more than $275 million. He wrote the password on a sheet of paper, that he lost. IronKey allows 10 guesses and he has already used 8. Thomas now has two more chances to enter the correct password or he’ll be locked out.

On Twitter Thomas classifies the incident as a “painful memory” and he wishes “others can learn from my mistakes.”

The New York Times reported that 20 percent of existing Bitcoin appear to be in “lost or otherwise stranded wallets.”

On Monday, Bitcoin fell more than 10 percent from Sunday. The cryptocurrency is up over 300 percent in the last 12 months.