Most touchscreens have more than two layers.
On most touchscreens there are usually two layers that make up just the digitizer. The glass on top that you touch and the actual digitizer sheet which consists of the touch matrix circuitry. The digitizer sheet is adhered to the glass so it often appears to be one piece. So you where correct to assume glass cover, digitizer and then lcd. The digitizer sheet and glass have a small gap that has an adhesive in it. On both the glass(bottom) and digitizer(top) is a transparent metallic conductive coating which is usually indium tin oxide. The human touch is conductive which allows for the electical sensors in the digitizer and glass sheets to sense the touch at a specific location.
Some of the newest technology such as Super AMOLED is able to get away from the two conductive sheets and has the touch sensors built into only one sheet, so these touchscreens would be an exception. So most forms of touchscreens consist of three or more layers.
I'm sure as time goes on the technology will change to allow for thinner touchscreen such as the super amoled.