There are some time situtation that your files in Pen Drive is not shown after you remove your pen drive from some other computers.
so getting your file back there is one command.
open your command prompt ( from start menu –> Run –> cmd.exe)
go to your pen drive ( may be e drive, f drive what ever check from explorer)
write there e: press enter
then write the command:
attrib -h -s -a -r /s /d *.*
and you have done.