All the photos disappeared instanly by themselves....

[Moltke]

I put Linux Lite 4.8 on my friends desktop computer and all went well.
He's been using the computer with no errors for four days now. He went to his Photos folder where I had placed several thousand of his photos of all types and the folder is  now empty. Not one photo was present. I had him go to the recycle bin and it too was empty.
He says he did not delete any photos but did up load more photos from a thumb drive. They uploaded with no issues.
I had him check to see if somehow the photos file was sent to the thumb-drive,they had not.
Any ideas as to what has happened to his photos or where they went?

It migth worth checking with some tool like photorec and see if it can find them.  Install the tool with

Code:

sudo apt-get install testdisk

once installed, launch the app by opening a terminal and type

Code:

photorec

and follow instructions from here https://www.cgsecurity.org/wiki/PhotoRec_Step_By_Step

Hope this helps!