I tried the retail 1.15 patch and when I try to activate it, the Voice over says cannot find game, even though I am in the main menu of the game.
Have you confirmed that your game version is 1.15? And is the name of you main executable 'Torchlight.exe'?
Now my other question is does the exe need to be in a certain location (directory, etc.) for the trainer to find the game, or does the trainer find a memory reference, not the exe itself.
Trainers search for the game process in the process list. If your game executable is with some other name, it will create the process under that name, which does not match the name the Trainer is looking for. Hence you might be getting "Trainer cannot find game" error.
Since I don't have the 1.15 version of the game, I am uninformed of the process name the trainer is looking for.