Toggle layer's visibility and reset previous active layer

Having a senio moment or a Monday morning crisis here. I'm trying to toggle a layer's visibility with a script (so it can be put on an keyboard shortcut with an action v. useful)

// toggle top layer
// app.activeDocument.artLayers[0].visible = !app.activeDocument.artLayers[0].visible;

Nice one liner, only works if the layer you want to control is at the very top.

// Switch off any dialog boxes
displayDialogs = DialogModes.ERROR; // OFF 


// call the source document
var srcDoc = app.activeDocument;

// current layer
var originalName = app.activeDocument.activeLayer.name;

var myLayerName = "that_toggle_layer"; //layer to be toggled

// select toggle layer
srcDoc.activeLayer = srcDoc.artLayers.getByName(myLayerName);

// toggle the (in)visibility
srcDoc.activeLayer.visible = !srcDoc.activeLayer.visible;

// select original layer, as it was at the start
srcDoc.activeLayer = srcDoc.artLayers.getByName(originalName);


// Reset any dialog boxes
displayDialogs = DialogModes.ALL; // OFF

So I'm a little confused as to why the longer snippet won't work. It should select by name the layer in question, switch ON the visiblity if its OFF (or vice versa)  and then, here's the trick, set the active layer BACK to the one at the start.

Only I can't see the wood for the trees this morning. Any help would be appreciated.