Finding “ghost” fonts in PowerPoint to replace them

Sometimes it happens that when saving a PowerPoint file, it displays a message saying that

Some of your fonts cannot be saved with the presentation.Cannot be saved: (font name)Reason: Font Not Available

The problem is that even if you use Replace Fonts... to replace the missing font with one of those installed on the system, the issue persists. It's as if the font is somewhere PowerPoint is unable to apply the replacement. Not only that: this “somewhere” is in a place where manually searching for the text element containing the font is unsuccessful. Basically, it's unclear where the font is.

Is there a way, perhaps using VBA, to find exactly where the font in question is and replace it with another?