Rule-Service-File; Actions --> Trace will only trace the activity and may miss some things like file info etc.
To trace the actual file listening piece, upload a file one and look at Requestors in your SMA. One or more of the requestors should have Client Address column containing your file listener's service package name. Trace those requestor sessions from SMA one by one by placing files one by one. Luckily, one should be your actual file listener session.