In a small bowl stir together oats and water. In a medium bowl combine the flour and baking soda.
In a large saucepan melt butter over medium heat. Remove from heat and stir in sugars, vanilla and salt. Whisk in the egg. Add the flour stirring just until combined. Stir in the oats and trail mix.
Let the dough stand for a least 1 hour, or preferably cover and refrigerate overnight.
Preheat the oven to 350º.
Drop one tablespoon dough on to ungreased cookie sheets. Bake for 10-12 minutes until the cookies are golden brown on top. (More time is required if the dough is chilled.) Remove to a wire rack to cool completely.