as vhg said above, but also
are you sure somebody hasn't logged the computer in under a different user or administrator
Also
try going to search on the start menu and search for files and folder then put in *.jpg and run the search, this will find all file that have the jpg extension which your pic probably will
If the drive has been wiped depending how important these files where to you it is still possible to recover the data, but you will have to take the computer to someone who has the equipment to do this, and it may be expensive. most important thing if you intend to do this is do not install or save anything else on that computer