Hi Doug,
There's not a way that I know of to automatically reset a node to its default values, but what you can do is add a new node of the same type via the Quick Node Palette (Tab key or "N" key) then either replace the existing node by connecting the input/output in your Node Network, or use the new node values as a template to manually reset the old node values.
It's a good suggestion and I'll add it to the feature request ideas.