If you've uploaded a file but not checked in (or these are checked out modifications), the files exists in the user's area so they should be able to redownload them say if the local cache is blown away. I do not know if admin can "recover" but they can certainly see them. I've explained scenarios like this to my user. Say your upload your work and then your laptop goes belly up. You can connect on a different machine, login and redownload that workspace with those uploaded files just fine.
If you delete the workspace on the server side, the files are gone kind of but the data is much harder to recover. They would be stored in the default cache vaults on the server (admin required) but has hashed filenames and certainly unreferenced files meaning they can be cleaned up at anytime. You would have to know what timestamps to look for or some key attributes since they would have to read files as text to recover. Not ideal as admin I would say not worth effort.
If the local workspace is still there, there is a chance files are there in cache folder as "lid" files. There is a tool around community that can reverse the filenames and export the files from the local workspace to a folder. I believe its destructive so make a copy of the workspace area. I cannot say offhand if deleting the workspace cleans these files up but I think it does.
