It's a typical USB Virus. It does 2 things - 1) hides your files 2) adds some viruses to the usb in place of the files. The files aren't deleted they are hidden.
Here's what you need. First make sure you have an up to date anti-virus software. when you plug in the USB make sure not to click on anything that pops up. Run a full scan on the USB and let it remove anything it finds.
Once that's done - Use a command window to unhide all the files.
Wow, great to know that we didn't lose everything on the memory cards - we tried of bunch of different stick and drives till we figured out what was going on.
Okay, now for the cleanup, would trend micro titanium be good enough for this job?