How to unhide folder in external hard drive

Hello,

My friend Hided a folder from my removable hard disk by using a software which he downloaded from google..I don't even know that software name...
He also deleted that software from my laptop
so now My Hard disk is showing 42 gb space used which is the size of my folder but when i open hard disk it is not showing any folder in it..
how can i Unhide that folder now...

it is very important folder
it contains lots of family pics

please help