We addressed that problem by actually placing a text file in the upload directory which had a name like (file_name)xfer_complete.txt. The contents of the file were always the same; something like "your file has been recieved and moved to a secure place on our network" if I recall correctly.
Most customers caught on right away, the others we would 'coach' if we noticed they needed it. We removed these files after a few hours, and our scp script was coded to ignore them.
Saved us a lot of those Sighs! :-)Just an idea to save some bandwidth for you and your customers. :-)
...the majority is always wrong, and always the last to know about it...