Mt. Gox was once the biggest exchange for the virtual currency.
But it filed for bankruptcy in Japan on Friday, saying it had lost nearly half a billion dollars worth of Bitcoins.
The company said it had found 200,000 Bitcoins, worth about $116 million, in an old digital wallet that had been inactive since 2009. But it was still looking for another 650,000 Bitcoins, valued at more than $390 million.
The missing Bitcoins represent about 7 percent of all the Bitcoins in circulation. They were worth about $480 million at the time they were reported missing.
Mt. Gox has been struggling for months, and it filed for bankruptcy protection in February.
At the time, it blamed hackers for stealing the Bitcoins.
But many people were skeptical of that explanation, especially because Mt. Gox had been facing financial problems for years.
Some people even speculated that Mt. Gox never had the Bitcoins in the first place and that it was using them to cover up its financial problems.
Now that Mt. Gox has filed for bankruptcy, we may never know what happened to all those missing Bitcoins.