Not the first time, and it will be FAR from the last.
Ramper does the download, waits to stack the upload and falls asleep. (NOT unusual at all, and a COMMON way to catch a nap, for at least 70 years!) Busy ramp, lots of bustle, no one notices he's gone.
Light upload, all goes in one bay, rushed ramper locks the hold without clearing it, and the guy is still blissfully snoring away inside. Sometime between takeoff power and rotation he wakes up and realizes he's screwed, and sits back for another nap, while trying to think of how he is going to explain this when he gets to the other end.
Next day, every sup and manager at the station gets called in for an emergency meeting, with just about the entire Corporate Safety Department there to greet them. Then the REAL schitstorm ensues. (ASK ME HOW I KNOW THIS....)
Everyone who has ever worked an airline ramp has an "I know a guy, who knows a guy..." story about this. It usually comes out right after the Lav Dumping stories, which usually comes out right after someone dumps a lav all over themselves.