By fonts, I'm assuming your mean "Text Styles".
The text associated with those styles could be "hidden" in blocks, dimension styles, complex linetypes, even empty text objects. (Yes, some people still manage to make them.) I would start with blocking the drawing into a clean file. That will eliminate any empty text objects, blocks, and anything else you can't select using window selection. Check to see if those styles are still there. If so, begin checking dimension styles and any blocks that reside in the drawing.