Normal Trip up.
If your using XP or Vista you may be able to do a system restore point after they where browsing the net before they cleared down the file. This is not for the faint hearted to do and I would not garantee the results.
Its all down to how clever the person is thats using the PC and how much time you want to spend digging.
Normally there not as clever as they think they are and miss something
Or are you speaking about someone locally looking at stuff on your PC?