Files going missing, CC files

We are having an alarming issue where files are disappearing out of cc.

We essentially have a collaboration folder of images, just jpegs in various folders within.

Last month within one of the folders around 50 images disappeared. I put it down to one of the collaborators moving the files out, I told everyone off and said to leave them where they were and we thought all was fine.

Today we note that another folder is missing literally hundreds of images.

Now obviously I am not a muppet and have back ups, but this is deeply concerning. Is there anyway to check on line history or changes or what ever to determine when and how these files just went away?