Hello,
To the best of my knowledge the files shown under UJFS are not actually saved in the file system. You can check and verify this. All sap related files are saved in specific directories. You can use t-code AL11 to check the diretory path for all SAP files. As far as I know the content of the files are saved in tables as blobs and they are found through unique ids. At least that is the way it used to be in the early days of BPC on NW platform.
Regards,
Leila