Where are the game save files in PC? Bluestacks (without opening bluestacks)
You can find  it at C:\ProgramData\Bluestacks\android\SDCard.vdi
You must show hidden files and folder at folder options to access ProgramData folder.
And you need a .vdi reader to open SDCard.vdi.
I used PowerISO (download it from Google) to open .vdi file.
Then open .vdi using PowerISO and search for your game. :)