Unable To See Files In Pen Drive : Fix It

Today, I went to the home of my friend and he showed me an 8 GB pen drive which was full of images, documents and movies but after plugging it in computer and opening it, there were nothing in it. Although through properties, I could see that 80% of the pen drive was full and antivirus also was showing that files were being scanned by it, but after opening the drive, it didn't show anything in