Sent 1 BTC to himself and ended up losing $740 million worth of Bitcoin! In August 2010, a user posted on the Bitcoin forum asking for help: he had purchased 9,000 BTC and sent 1 BTC to himself. Before the transaction was confirmed, he closed his wallet. After restoring an old wallet backup, he found his balance was down to just 1 BTC. The remaining coins had been transferred to a new address he didn’t recognize, and the key to access that address wasn’t in the old backup. He wrote: 'The old wallet file is gone forever.' 16 years later, according to Arkham data, that address still holds 8,999 BTC—worth about $741 million. Everyone can see it, but no one can touch it.