Detecting a layer by name

The following code is part of a larger script. I'm trying to detect if the layer "Canons Grid" exists. If it doesn't then create a new layer with that name. This code fails everytime, even if the layer doesn't exist. What am i doing wrong?

var doc = app.activeDocument;
var canonLayer;      
      try {
                  canonLayer = doc.layers.itemByName("Canons Grid");
            }
            catch(e)
            {
                  canonLayer = doc.layers.add({name: "Canons Grid"});
            }