Missing Font: Where in the story...?

Story: A very long (2.5 hours) course module inherited from a retired colleague. The course has multiple scenes, each scene has several dozen slides, and many slides have multiple layers.

Need: Locate the offending slides which use two missing fonts.

I am familiar with the "find and replace font" feature (and it works brilliantly) but because of the complexity of this course, I am not able to successfully use that "search and replace" feature - I just cannot find the replaced font (I used Webdings for visual simplicity).

Does anyone have any effective hacks that they have used to find the actual instances of a font in use that is not installed on the system that is trying to work on a course?

Thanks all!