Because you can't see the file I'll assume the file is being hosted (FMS?). In that case you cannot copy/attach/save the file. It would be a violation of FM hosting security to be able to get a copy of a hosted file without using the admin-console, which requires admin access.
BTW, when you do get access to the FMS computer do not copy the open file in the database folder until after closing it. Copying files open on FMS will almost always corrupt the original. The copy is probably corrupted and incomplete as well so you can't use it either.
Thank you for your post!
You might see how can I email something in a container field?, which seemed to be answered with an option for this.
Also, I am going to move this thread from the FileMaker Community Feedback Space, which is specifically for input on the Community itself, to the Discussions Space where you should receive more views and potentially more advice!
What you are trying to attach is not a FILE. It's just data in a container field. First you need to create a file to attach.
In your script, add
Set Variable $FilePath = Get ( TemporaryPath ) & GetContainerAttribute ( YourTable::YourContainerField ; "filename" )
Export Field Contents ( YourTable::YourContainerField, $FilePath )
Then in the Attach File area, you'll just use $FilePath as what you want to attach to the email.