Where's my tonnage?

[Siegeswimpel]

With my initial attack on a convoy, I used all five torpedoes & successfully sank three merchant ships. After evading detection from the escorting warships, I noticed that one of my targets was stationary & slightly stern down in the water. Although I had two torpedoes left, these were inaccessible in external stores due to bad weather.
I knew I’d damaged the C2 &, as I was under no pressure to move off, I decided to hang around & watch it hopefully go under. 29 hours later, (winds still doin’ 15!) 5th October 1941 4:10 am it finally sank. There was no ‘Enemy unit destroyed’ message & nothing entered in the captain’s log!
I can only assume that if there’s too much of a time delay, don’t bother waiting around ‘cos you won’t get the tonnage.