I'll explain what happened. Running that game, the software was unable to create the .SAV file for some reason (unsupported characters??) and it got stuck in the process of creating the file. By turning off the console you corrupted the file and the entire SD card. A similar thing happened to me 2 times, using the r4 gold pro's own software. With YSMenu it has not happened again.
Unfortunately you have to format it and re-copy its kernel and roms.
Note: Probably if you insert that card into the PC, you will see that it will not be able to read it, or that will contain one or more files with random letters and gibberish symbols.