Why my pendrive sudden lost the data?

[Low Swee Mee]

Thanks for help me to solve the problem!!!

 

[nhasian]

your pendrive itself may have become corrupted. if you have data you need to recover you can do that with
testdisk http://www.cgsecurity.org/wiki/TestDisk
and
photorec http://www.cgsecurity.org/wiki/PhotoRec