Missing track but still hearing it

Hello everyone.

I'm doing the sound design for a short film in Audition and just now a whole track has disappeared but I can still hear it!!! The track has an effect on it for different songs to sound as if they are coming from a speaker in the room. I thought it might just be hidden, but as soon as I mute any parallel sfx going on the Mix track stops showing any gain, as if there was nothing there, but the song still comes through with the effect on it!

Any ideas on what could have happened? I've quit and reopened twice, the song still plays but no sight of the track.

Thanks for your time! 🙂