Pen drive usb problem

i have a problem and this one i think is rare.

i thought my USB pen drive was fine until i try to copy some files successfully then safely remove it. and then when i try to plug it on my computer at home files aren't there and the consumed space is back from its original size, also the old files are there and readable.,

The main problem is i copy some files successfully and then vanishes after i removed it safely.,
Its not a shortcut virus that hides files., its different.,

old files from my usb is fine and readable, but after i delete it., it is still there when i plugged it again.,