Blackstone Inc. (NYSE:BX) has emerged as a suitor for Appen Limited (ASX:APX), which was briefly subject to a $1.2 billion buyout proposal from a strategic suitor before they walked away. DataRoom understands that private equity firm Blackstone had been running the ruler over Appen with a view of making a bid for the firm, before a profit downgrade in May. It's unclear whether it's still interested.