I never deleted any of them... i pulled the flash drive out of an Imac at school as i rushed out the door and when i went to my next class (win7 pc) all the files were gone but it still showed that the data space was being used by something.
Do you need the data immediately? Sometimes this happens to me too when I switch files between my mac and pc. For me it was because my pc couldn't read the partition format while my mac could. So while it would appear in my mac it wouldn't on my pc. What I had to do was go back to my mac take out all the files and reformat it to fat32 and put all the files back on and it would appear. I don't know what else to tell you
Or may the files are hidden. Sometimes like a period or underscore in front of the file name hides it in either mac or pc... go to control panel>Folder options>view
select show hidden files and drives and apply. Check the drive...