Bitcoin has recorded historic growth after increasing 92% in a month and around 340% in a year, but one investor is locked out of accessing his riches because he forgot his password.

German-born programmer Stefan Thomas told the Times he forgot the password to IronKey, an secure flash drive has access to 7,002 Bitcoin — $220 million worth. IronKey gives users 10 guesses for their passwords before seizing its contents.

"I would just lay in bed and think about it," Thomas told the New York 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 many investors get rich, some have had trouble accessing their Bitcoin investments due to forgotten passwords, according to the Times. The paper reported 20% of existing Bitcoin "appear to be in lost or otherwise stranded wallets."

Some high-profile investors remain wary of Bitcoin's surge. UBS analysts said cryptocurrency volatility does not make it a "suitable alternative" to safe-haven assets. Billionaire "Bond King" Jeffrey Gundlach said bitcoin hit "bubble territory" once the price passed $23,000.

Even after sliding as much as 21% over Sunday and Monday, the price of Bitcoin has recovered back to around $36,000 the next day.

"Shark Tank" star Mark Cuban compared the "cryptos trade" to the dot-com stock bubble of the 1990s.

"Watching the cryptos trade, it's EXACTLY like the internet stock bubble," Cuban said in a tweet. "EXACTLY. I think btc, eth , a few others will be analogous to those that were built during the dot-com era, survived the bubble bursting and thrived, like AMZN, EBay, and Priceline. Many won't."

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