Hello, polop... I'm not going to take the time to examine each of the pests and their usual actions. I know of malwares which deliberately search for and delete jpg and vid files. Damage is done. I can give you another forensic tool [free] which will scan your disk thoroughly and find files [if they exist] even in deleted partitions. But not if they have been overwritten.... nothing can help then.
By the way... and I know that you have heard this advice before, but now there is a hammer behind it to drive it home... BACKUP!!! It's not as if it's a chore.... once you set it up it is automatic, in the background, no finger lifting required.
First thing to do when stuff vanishes is to check with cmd.exe's dir command, just in case it is a simple case of changed attributes.
Get TestDisk 6.9 ... It's not a simple tool to learn and run, but it works. If it doesn't find your missing files, then just accept that some lessons are hard. Beware!! that pgm can destroy your installation if you misuse it. So think before you press buttons... it does not ask for confirmations.