Make sure the file isn’t already in Finest or X drive first and be aware that whichever team has received the file may well resend it as that is the agreed process – this would result in a duplicated rather than missing file number – if this does happen at a later date then the duplicate file can be deleted from the X drive.
If the school has ticked the option to archive files it should be in DTSApps\Outgoing\Archive.
Copy the file back to DTSApps\Outgoing then choose to Rename and remove the datestamp prefixed to the file name eg rename 201905031155280615_878xxxx_8782718_dt_190503_1154222.381 to 878xxxx_8782718_dt_190503_1154222.381
Do not change the extension or edit the DTCS2006 node.
Use DCC apps>Reformat for FMS, check the File Type is DTCS Finance and the path is DTSApps\Outgoing, then Begin Transfer