STORY: ::FileSouth Korea’s Bithumb crypto exchange has apologized for a $44-billion mistake, after accidentally giving away 620,000 bitcoins as part of a customer rewards campaign.The company said it had restricted trading and withdrawals for the 695 affected customers shortly after the error on Friday.And that it had recovered 99.7% of the bitcoins as of Saturday night.The exchange had planned to distribute small cash rewards of 2,000 Korean won, worth about $1.40 , or more, to each user as part of a promotional event. But instead, winners received at least 2,000 bitcoins each, media reports said.In a statement, Bithumb said the incident was unrelated to external…