While the Bitcoin price has recorded historic growth – increasing by 92% in a month and about 340% in a year – one investor is locked out of accessing his riches because he forgot his IronKey password.

Stefan Thomas, a German-born programmer in San Francisco, told The New York Times this week that he forgot the password to his IronKey, a secure hard drive with the keys to his wallet with 7,002 Bitcoins, or about $US220 million ($280 million) worth. IronKey gives users 10 guesses to get their password right before encrypting the hard drive’s contents; Thomas has two more tries left.

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

As some bitcoin investors get rich, others have had trouble accessing their investments because they have forgotten their passwords, The Times reported. About 20% of existing Bitcoins “appear to be in lost or otherwise stranded wallets,” the report said.

Some high-profile investors remain wary of Bitcoin’s surge. UBS analysts said this week that cryptocurrency volatility did not make it a “suitable alternative” to safe-haven assets. And the billionaire “Bond King” Jeffrey Gundlach said Bitcoin hit “bubble territory” once the price passed $US23,000.

Even after sliding as much as 20% over Sunday and Monday, the price of Bitcoin recovered on Tuesday, rising to about $US36,000.

In a tweet on Monday, the “Shark Tank” star Mark Cuban compared the “cryptos trade” to the dot-com bubble of the 1990s.

This article first appeared on Business Insider Australia, Australia’s most popular business news website. Read the original article. Follow Business Insider on Facebook or Twitter.