When moving files you have to first store your Container data in your file. Then you move the file and then set it up to be stored externally again.
Are you sure of your path?.
Perhaps you have created an alternate path but the default path is
Library > FilemakerServer> Data > Databases >RC_Data_FMS >"FileName" > Files > "FileName" > then whatever table structure you have created ) .
The server backup can also back up these external storage locations, have you set this up?.
There is no need to import the external storage into the file before moving the file, providing you keep the relative paths (database to external storage) the same you can drop them back in at will. Importing large amounts of external storage container fields into a database can push the file size beyond the (what used to be the maximum size, not sure if this still is the case) file size "downoad database" command in server admin can handle.
I am sure about the path as it is storing the images in the specified folder.
I have set this up in the admin console Folder area.
Removing the data file from the server is deleting the externally stored images. This does not show any warning either which makes it too risky .
Here is a similar link .
Pretty sure this is by design because the external RC data really belongs to the file, they are not separate in a conceptual sense. The RC feature is just for FM to manage where to store the data from a container.
If you had embedded the data in the container and removed the file you'd also not have the container data anymore. You wouldn't get warnings either.
When you download or upload a file, the RC data files go with the main file. Did the local file that you uploaded not have RC data locally?