[Sluttypatton]

Had you added oil recently? It sounds stupid but it is really common, people spill oil on the block and it burns off, causing a little bit of smoke. Anyways, I wouldn't worry too much about it, just keep your eye on it and see if it happens again.

As for the head gasket, I suppose it is possible that if it were damaged in the right place it could leak coolant or oil onto the block which would then cause smoke, but it is pretty unlikely.