Can't find Audio in slide layer

In my course, I have quizzes and when a user selects their answer for a question, the slide layer will prompt whether they've selected the correct or incorrect response.

However, when I preview the course, an audio file of an earlier developed version of the course plays of a narrator saying "incorrect" or "correct". I want to delete this audio file, but when I select the slide layer that it is on, no audio file appears in the timeline. There is also no audio graphic on the slide indicating that there is audio on the slide in the first place. 

I can't attach the course due to confidentiality reasons, but would appreciate any suggestions!