My 4gb integral flash drive can no longer be accessed?

My 4GB Integral flash drive has 2 partitions, the second of the partition contains the executable file used to unlock the first partition of a much larger capacity (where I have my files kept), unfortunately this unlocking file was mistakenly deleted by an antivirus program. How can the unlocking file be restored or recovered?. I have checked the recycle bin and other parts of the system, the file could not be found.