Its difficult. But here is what you can try.
You should be able to get the last file that was checked in and intact in old oracle dump. Refer Application_data and fvitem table.
In fvitem you will have uniquesequencenumber convert that to hexa decimal and look for that file in the vault dir.
So after that timestamp whatever file that is available in you vault is the delta you lost.
Now, you have a smaller set of files from which you need to find out what exact file it is. Which is very difficult.
Try opening in Notepad or something and look for some signature. Suppose you think its a pdf file, just change that particular file to pdf extension and try to open it. If you can make any sense of it, you are lucky. But the history all those stuff is gone.
You need to rebuild everything manually again, but as long as you have the file, it might help a bit. But its manually time consuming work and not sure how for you can get the data integrity back.
Hope this helps. I guess your process to backup is fixed atleast now 🙂
