Last month, the price of bitcoins hit an all-time high, over $20,000 each. This was both a promising and infuriating development for German software programmer Stefan Thomas.

Thomas, who lives in San Francisco, has a digital wallet stuffed with 7,002 bitcoins worth over $220 million. The only problem? He doesn’t remember the password.

According to the New York Times, Thomas stored the bitcoins on an IronKey hard drive in 2011 that gives users 10 guesses at the password before they are encrypted forever. So far, he’s used eight guesses. He lost the paper with the password written on it the same year he got the bitcoins.

“I would just lay in bed and think about it,” Thomas told the Times. “Then I would go to the computer with some new strategy, and it wouldn’t work, and I would be desperate again.”

Making matters worse for Thomas, the price of bitcoins continues to surge, hitting $37,000 last week before falling this week after a number of holders sold theirs.

Perhaps wisely, Thomas isn’t letting himself get antsy. He’s placed the hard drive in a secure facility and plans to wait until cryptographers can help him crack the code in the future.

“I got to a point where I said to myself, Let it be in the past, just for your own mental,” he said.

An estimated $140 billion in bitcoin has been lost or locked away due to forgotten passwords.