I have many folders and files saved on a NAS that are normally indexed in groups in DTP.
Often, to add a new file, I drag it from the Desktop to the corresponding group, and DTP indexes it after copying it to the right folder on the NAS.
Unfortunately, I realize that when the NAS was accidentally turned off, the folders and files were copied directly to the DTP database, without being saved on the NAS and indexed.
Select the item in DEVONthink and choose Data > Move to External Folder. This will move the file to the indexed parent group in the Finder (a process we call ‘deconsolidating’, incidentally).