Well.. here's a slightly clumsy idea which might do the trick.
End the script with a link: "click here after the file has successfully downloaded". It's then up to the user to check he's got the file OK before proceeding.
The script activated by the link could proceed directly to whatever it is you want to do.
Or, you could upload the file back to a temp folder in the server, and check the filename/size or whatever against the original before proceeding.