We've all done it, no worries!!
My criteria for "best investment ever" are slightly different. As K-ice points out, there's a question as to how to get in on these opportunities. From the article, the stock's 78x jump emerged from some sort of bankruptcy reorg (?), something where it would be hard for an outsider to know in time, even if the stock is available for trading. Similarly, I remember reading about BTC when the first two pizzas were bought, but had 2 barriers: I was too skeptical that this new thing would grow to be of real value, and I would have needed to learn how to access it and mine or buy it, which was difficult (at least relative to "I'll buy a share Company X that trades on NYSE"). Actually I can see a case for BTC meeting the title's implied definition, but am happy to set it aside for this thread. So my criterion is, what's the best investment an ordinary Main Street investor could have bought as easily as buying a stock on a major exchange?
I have 2 well known candidates. Neither got 78x as fast as the example you gave, so your find beats them % per year, maybe it's the best under that measurement. But 78x isn't sustainable anyway so maybe a higher return over longer time is a better metric. What's the best you could do over 10 years, 20 years? Are there widely traded stocks that meet my ease of purchase criteria and exceed 78x?
Depending on timeframe:
10 years - TSLA. Available $15/share ($3 after stock splits) in July 2010 shortly after IPO. Sold between $1080 and $1795 ($216 and $359) in July 2020, so you could have done 359/3 = 119.7x in almost exactly 10 years. It's up quite a bit since then too - over 200x at current prices. To be fair, prices were usually between $4 and $6 (I mean $20 and $30 before splits) most of the first year but 120x from then to now was achievable on many start dates.
https://finance.yahoo.com/quote/TSLA/history?period1=1277769600&period2=1619049600&interval=1mo&filter=history&frequency=1mo&includeAdjustedClose=trueI remember wanting that Tesla roadster, and during that very year, buying a foolish new car. I have wished many times that I thought to buy a used car and put the other 25k into Tesla. Even if I sold half in 2020, I'd be ahead by about, well, 78x! Meaning a couple of million bucks.
20 years - Apple. Early 1997, frequently available around $17/share (.15 after stock splits that turned one share then into 112 shares now), and at least one point, about $13.50/share (.12 after splits, according to Yahoo Finance tables
https://finance.yahoo.com/quote/AAPL/history?period1=345427200&period2=1619049600&interval=1mo&filter=history&frequency=1mo&includeAdjustedClose=true). By early 2017, $35 after stock splits, so roughly 228x over a 20 year period. Again has done well since then; at current price $131.94/share, up roughly 900x since early 1997.
The company had been widely traded for 16 years by the start date and performed mediocrely so the trick was knowing when to pick the flailing company right before its turnaround became evident.
ETA: Just realized that 20 years ago to today is better than the timeframe I picked if you want an exact period. Up around 300x.
At 50 years, of course the pick that's obvious in hindsight in Berkshire. Famously up 2000x or so over time. I have a little trouble understanding how one became a shareholder of Buffett's Berkshire back then, though, other than being a Friend of Warren.