Both the Mouse and Touch objects allow you to pass a layer parameter for the X and Y expressions. This is very useful if you scale or rotate layers.
e.g. Mouse.X("Layer 1") returns the mouse's X position on Layer 1, taking in to account its parallax, scale and angle. If you use only Mouse.X, it does not take in to account parallax, scale or angle, so the result can be wrong.
In your case it would be Touch.X("Layer X") obviously, or Touch.X(0) for layer with index 0, but this should be what you're looking for.