same thing happened to me in my last two patrols. In the last one I potted a merchant in convoy with two and it sank on the spot in a fairly short space of time, and though the sea was quite rough it wasn't mountainous. Never got any credit for that, even though the escorts came looking for me.
Then I downed a merchant in harbour with another two eels, smooth sea, and that vessel died from a broken back. I did get recognised for that, yet the patrol boat ignored me and just kept patrolling. It was quite odd behaviour really. The patrol craft came by at its normal cruising speed, stopped near the stricken ship, then reversed and returned the way it had come, but made no attempt to look for me.
My last torpedo just nicked the stern of an ore carrier which carried on sailing without any signs of distress, so I doubt I could claim that - but all I got for my efforts was renown for the harbour vessel. Hmph.
