When you're having a one night stand and the girl's performance is lacking and unsatisfiying you leave a Stealth Torpedo in order to let her know to step up her game. After the unsatisfying sexual experience the unimpressed man takes a shit in the bed of the girl while she is in the bathroom or shower after her poor showing in the horizontal tango. Then the man dresses quickly and leaves before she comes back into the room. If the man is a brave soldier than he will sit outside her window in order to hear the anger/repulsion coming from her bedroom as she discovers the torpedo has struck her bed with a direct hit which usually results in a hearty belly laugh coming from the male.
Tom was so unimpressed with Sarah's performance in bed, he had to give her a stealth torpedo to let her know to try a little harder next time.