Will not start

Drove to friend's house just fine. Couple of hours later, went to leave and would not start. Turning key lights up dash instruments. Windows, radio etc. All work but not even a "click" to the engine compartment. Tried rocking it in gear, no help. Truck has removable security "key" which was looking grimy so cleaned it and the receiver with alcohol but did not help. Could it be the starter? I thought I would get a "click-click-click" from the starter if that was the problem but the is absolutely nothing (except the fuel pump running for a few seconds). The ignition key itself? Help!