The only way to hide layers in the timeline is to use the Shy switch. If you disabled the master Shy button at the top of the timeline and made sure the audio layer is not there somewhere (perhaps at a different time zoom level?), then the only thing I can think of is that the audio could also be in some video layer that it's also in your timeline? Before CS3, audio playback required building previews, so just in case - Have you tried Edit > Purge > All?
Thank you for your response, I have purged all. Shut down and restarted. Made a copy and the problem persists. In the "junk: copy I eliminated all sound that appeared in the regular and "shy" layers. With NO sound appearing in the timeline - it still plays. That it might be attached into a video file, and thus not seen as an audio layer is possible, since the sound layer was actually a compound of sounds made in AE and then copied into a QT movie. I believe it is the QT movie that is playing, but not appearing. Maybe, as you suggest it is hidden as a Video. Thanks again. Puzzling 10 hrs on this.
Barry, try this:
1. Make sure the master button for Shy is turned off at the top of the timeline panel (ie, the guy's face is visible).
2. With the timeline panel active, Select All layers (Command+A).
3. Press LL (L key twice ).
That will reveal audio waveforms for all layers. This should make it easy to identify the double agent.