I've googled, but came up with too many options/results and I'm not sure which to trust, so I turning to the forum, assuming someone will have some decent knowledge on this.
I've got a flash drive (64GB) that essentially contains all of my family photos.  (I was recently reducing dupliates in an effort to consolidate, then, once organized, copy to a backup drive).
So, for our Christmas card, I was pulling out some family pics from 2014 to build our Christmas card.  All of a sudden, many of the files in several folders, were 'gone'.  The flash drive is still accessible and I'm viewing everything as 'unhidden'.  Quite a few folders appear blank, as in 0 files, 0 bytes - not just the 2014 folder that I was pulling from, but also 2013, 2012, etc. back to about 2007, but 2006 and prior seem okay.
Its a 64GB flash drive.  When viewing properties of the entire flash drive, it shows 59gb filled.  When I view properties of the main directory 'Photos' within, it shows 7gb.  The 59gb gives me reason to believe I can recover the files, but really need to know the best way to do so.
I'm concerned that if I 'try' something that isn't necessarily recommended that I could dig myself a deeper hole.
Any suggestions?  Any experience with any specific programs?