Recovering a file that was sent via FTP is unique to a file sent over other Ports or Protocols e.g. SMTP/25, SSH/22, HTTP/80 etc, because FTP sends the file over higher ports that create a new and unique Session ID.
Port 21/tcp FTP Command Session
Port 20/tcp FTP Data Session
In the attached PDF document, Session ID 171651750 negotiates a FTP session tcp.dstport 21 will use tcp.srcport 46736 to transmit the file.
This creates a New Session ID 171653117 using port 46737 to Port 27327 as agreed in the first session.