using drop box? –
If the original .DATA folder is backed up somewhere, you should be able to recover it – by creating an empty text only file with the same name as the .DATA folder, ending in .enl (so for library.DATA, a file called library.enl)residing in the same folder as the the .DATA folder (not in the .DATA folder). But if that .DATA folder was overwritten – it is toast.
So move it out of the drop box and see if you can recover it. Everything you need (groups, PDFs etc) are in the .DATA folder. The .enl file is really just a pointer.