Back in November 2013 we reported the story of James Howells, who mistakenly threw away an old hard drive containing a bitcoin stash worth £4m. Now, as the cryptocurrency once again soars to new heights, stories of early investors and bitcoin miners missing out on life-changing fortunes are back in the news.

This time it is the story of Campbell Simpson, editor of the Australian version of the Gizmodo technology website. Back in 2010, when bitcoin was worth practically nothing, Simpson invested AU$25 ($18.70; £14.40) out of curiosity and became the owner of 1,400 coins. At the time there was very little use for bitcoin, barely anything to spend it on, and no clues as to what its future would hold.

Two years later, Simpson recalls in an article for Gizmodo, he threw away the old and failing portable hard drive containing an encryption key which is the only way for those bitcoins to be accessed by anyone.

Today, with bitcoin's value surging past the $2,600 mark (A$3,500; £2,000), that simple text file and the coins it unlocks would be worth $3.6m.

The value of Simpson's lost bitcoin began to rise almost as soon as he threw them away, putting the 1,400-coin kitty quickly up to $3,000, enough to pay off the debts from a recent holiday to Japan. "It wasn't a big deal", Simpson recalls. "It was one of this 'aw, s**t' moments that happen to everyone on a semi-regular basis. I got a parking ticket, I forgot to send a birthday card to a friend overseas - that kind of thing. Without the benefit of hindsight, of course, it wasn't that big a deal...bitcoin was a fun fad."

Despite friends and strangers alike offering Simpson advice on how to possibly find the discarded hard drive - "apparently landfill is exceedingly well organised and stratified" - Simpson has admitted to himself he won't get the coins back. "I don't even especially want to find those bitcoin, though. I'm really happy with my life at the moment. I don't need them. I'd like them, sure, but I don't need them...That chapter of my life is over."

And what about Howells, whose bitcoins were hurled into a south Wales recycling plant in the summer of 2013? Those 7,500 coins, mined by Howells when the currency was almost literally worthless, are today worth $19.5m.

At least he seems in good spirits about it: