Virus can easily affect USB flash drive when it gets in contact with infested system. Sometimes the virus can ghost the files and folders you saved to it. Whenever you open the flash memory stick it is empty yet there is indication at your computer drives list some part of the USB is used by saved information to it and they are still there while you cannot see them.
The problem is mostly caused by Recycler and other strain of computer viruses. When this happened to your USB the first thing to do is to scan the system and removable drive for viruses and remove them. On how to remove malicious software from your system visit this LINK.
After removing the viruses the next thing is to set Windows to show the hidden files and folders. To do that visit this LINK (This process also applies to Windows 8 operating system) .
At the end if you cannot see the hidden files and folders take these following steps to recover them. In this process we are going to resort to the use of free third party software that can do the job with ease. The name of the software is USB Show.
Image of the USB Show official page showing Descargar
STEP 1: Visit the software creator official page at this LINK. For your information, the page is in Spanish. To download it click on Desscargar (it is little down the page).
Image showing how to unzip compressed USB Show File
STEP 2: Unzip the file and double-click on the installer to start the installation.
Image of USB Show English in Windows 8
STEP 3: Click on 'English' to select English language.
Image of Recovering hidden files tab in Windows 8
STEP 4: Next click 'Recovery the hide files'[sic] to recover hidden files and folders.
Image of Browse For Folder showing USB drive in Windows 8
STEP 5: At the 'Browse For Folder' dialogue select your removable drive(your USB flash drive) and click 'OK'.
Image of USB Show recovering files and folder in Windows 8
STEP 6: Wait for the software to recover your hidden files and folders.
Image of USB Show completing task dialogue in Windows 8
STEP 7: After that click 'OK' at the USB Show dialogue to finish proces.