"I have tried ctrl F in explorer, with no results - even on files I know are on pc"
Yes, the search facility is excellent but it does have a few quirks to catch the unwary :-)
Because of the strange (to my mind) hierarchical arrangement of folders, searching the C drive will not find files stored in the Users' folders. You need to search those folders specifically. If in cleaning up, you're son moved the folder (which would explain why the undelete couldn't find it) he may have moved it into one of the users' folders. These are only searched by Win7 if specifically selected:
Open Explorer
Double click a User Name
Type in some text to search for it.
(As an example, stuff that I download goes into Rojash/Downloads, if I search Rojash, I can find it, but if I search the C drive, I can't).