The patch updating Metal Gear Solid V: The Phantom Pain to Version 1.06 has just been released, and fans have found out you can now get Quiet back after losing her in Mission 45: A Quiet Exit. At the end of this mission Quiet would disappear into the desert, after which she was gone for good. But not anymore.
With the latest patch installed, replaying Mission 11: Cloaked in Silence will give you the option of reuniting with Quiet. At a certain point (some say you’ll have to replay the mission 7 times) the mission description will change to [REUNION] CLOAKED IN SILENCE, and Quiet will return to Mother Base after completing this mission (provided you don’t kill her of course). You also get to keep everything you already unlocked for her.
Image source: Reddit