Mystery Sub Loss?

Here’s a puzzle.

In the records of the German navy command South (Marinebefehlshaber Sued – Admiral Weichold), there’s a telegram from a chap called Ahrens, who was assigned to the Regia Marina‘s torpedo boat Orsa, about a successful attack by Orsa on a submarine. Based on the report about the attack in the same file, Orsa was equipped with the German sonar equipment and depth charge launchers (see this older post), and Mr. Ahrens was an offiicial responsible for the final hand-over of this equipment to ships’ crews, and participated in the mission.

The text of the telegram is as follows:

131 Trapani 725 34 TF 8 1941

German Naval Command, Navy Ministry Rome

Entered Trapani with Orsa on 8 January 17.30 hours. Submarine attacked with visual success. Depart 8 January [should be 9?] 08.00 hours for Messina. Request information of Fuerbringer Berlin. Ahrens.

The separate report states that the attack happened on 7 January, at 09.45 hours. The target was identified as a submarine because of the very clear echo. The visual confirmation of success consisted of an oil spot on the surface, coming after a depth charge attack, an air bubble, and wooden pieces coming up.

Now here’s the puzzle. No submarine has been reported lost in the area on the 8 January or on the preceding days. One submarine went missing during this period, HMSub Triumph, but that was probably far away from Trapani, in the Aegean. More detail on this can be found at this link. HMSub Triumph was quite an interesting boat, having been involved in Operation FLIPPER, the raid on ‘rommel’s HQ’ (actually offices of the Chief Quartermaster Panzergruppe). And her successor in name is busy again in Libya today

Of course, it could be that even though visual confirmation of the success was obtained, the boat attacked was only damaged, or maybe not even that. One boat that was in the area just prior to the attack was the famous HMS Upholder, which on 5 January 42 had sunk Regia Marina sub Ammiraglio Saint Bon during a supply mission for North Africa.

So, does anyone have any ideas who was attacked by Orsa on the 7 January, if anybody?