There is a good chance they haven't been deleted, their file attributes may have just changed to hidden or system.
Check to see if that is the case please. Open Windows Explorer and locate the folder where the files are stored. Then change the Organize ... File and folder settings as shown here:
View attachment 4641
If they really aren't there any more then you can return the settings to the way they were.
...
If the files are there then what anti-virus software do you use? and have you run a full system scan for viruses lately? Viruses can set screwy attributes for files but I have also heard of McAfee anti-virus itself having some weird issue a while back that used to cause something like this.