You may also want to do that for ...
ATTRIB -h *.jpeg /s
and
ATTRIB -h *.BMP /s
JPG is the most common spelling but JPEG is also allowed these days so you may not have any of them but it doesn't hurt to check and BMP is relatively old but you may have a few.
I am still a bit concerned as to why they would go hidden because I'm not familiar with any reason that would happen through normal use. I would recommend you install malwarebytes (the free version), allow it to update to the latest and then run a complete scan. A link to Malwarebytes can be found in our
Freeware DB.
I would also run a complete scan with whatever anti-virus software you have installed; if you don't have any then pick up Microsoft Essentials from the freeware DB as well (it's not perfect but it is far better than none at all).
If Malwarebytes or your AV refuse to install or run that is often a sign that some nasty malware is actually hiding out there blocking them so please let us know if that is the case. If so you will also need RKILL to terminate them first.