You may have noticed that when you export a DWG file, Revit temporarily creates PAT files in the export folder, and then it deletes them, just leaving DWG and PCP files.
To recover the deleted PAT files, you can simply use the program Recuva!
I'm not sure how well this works for network shares or NAS devices, but it should definitely work if you export the DWG to a local drive and immediately recover the PAT files (before doing anything else).
Pretty tricky huh?
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Recuperar os ficheiros *.PAT gerados pelo Revit | Truques e Dicas | Revit | Blog