I guess you have been at periscope depth - not at 40 meters as you assumed - and you rammed a trawler or DD or something, this destroyed your periscopes and other upper stuff. You won't get a message in that scenario. In these early days your hydrooperators are quite unexperienced and may have missed a slow moving trawler. And there are deaf spots at your bow and stern.
In the case of beeing depth charged or hitting a mine you would have been dropped out of TC.
I once hit a little freighter from Portugal right outside of Wilhelmshaven. It was sailing with 2 kts or so and couldn't move out of my way in time. Result: port diesel destroyed and heavy hull damage.
My crew even reported that freighter, but I ignored it so close to my homeport.
It was a very short trip.
