Something similar happened to me in one of my early missions (ST. Petersburg Blockade).
I was in a Kilo, waiting for that WASP to sail by. Fired a bunch of torps at it - all of which missed for a variety of reasons (bad TMA, bad presets etc.) Eventually, after wasting a lot of ammo I attracted the attention of the escort (a Burke) who turned around and began charging in my direction to check out the idiot making the racket. (I had a bit of a Perisher moment here, watching him approach on my scope)
So I think to myself "I bet if I fired a circling torpedo in his path he will run right into it and sink himself"
Feeling proud of my own brilliance, I loaded my torpedo, set the presets, gave myself a satisfied nod and fired the thing. It duly shot out off the tube, went a couple thousand yards, turned around and came right back to sink me
There was a saving grace here - my sub showed up under my Kills column on the Mission Status screen. I guess a kill is a kill, even if it is only yourself...