Turkish prosecutors on Thursday launched an investigation after the Istanbul-based founder of a cryptocurrency exchange froze trading and left the country holding a reported $2 billion in investors’ assets. The Thodex exchange suspended trading after posting a mysterious message on Wednesday saying it needed five days to deal with an unspecified outside investment. Turkish security officials then released a photo of Thodex founder Faruk Fatih Ozer going through passport control at Istanbul airport on his way to an undisclosed location. Local media reports said Ozer — reported to be 27 or 28 ….