I assume you want to find all text that is not using a specific style, rather than all text that does not use any style. There is no way to do this directly, but you can cheat. For the style you want omited from the search set one attribute to be different from all other styles. Since there are many attributes you can set, there is likely one that is common to all styles becasue you never changed it from the default. SOme common ones are Language or Skew or Vertical Scale in Advanced Character Formats. Change one of those for the style you don’t want found, then search for any text that’s different from that. For example, set the style’s Vertical Scale to 90% then search for Vertical Scale = 100%.
Thanks Scott, what a great workaround.