Altium Designer Deleted schematics completely
Find the original project directory (not the one listed in alitum). If the files are gone from there then check the hard drive and do a search for all schdoc files. If the file is not listed there then you have a problem.
In addition altium can be configured to save files in a history directory in the project folder. This doesn't come by default so if you didn't do that then the history files won't be of much use to you.
If the files really aren't in the project directory then they probably are gone you should see how bad you want them and pay for recovery (which may or may not work if the files have been over written, keep in mind that the more you run the drive the better chance that they have been over written).