Gotta assume it's a bug. IIRC I too have got a medal after 2-3 patrols with no renown earned/rewarded, or that particular medal is awarded on completion of a certain number of patrols. Of course SH3 only knows when you load a mission and when you dock, it can't keep track of your movements.
Was he rewarded an extra renown? (between leaving port & docking)
__________________
|