Where is that phantom audio?

I recorded a bunch of vocals for my project, they span 3-4 tracks and about a dozen take lanes each. I used Melodyne on some of them. I am now tweaking the details (getting syllables lined up, normalizing levels, all that) and somehow now have a phantom vocal track playing that I can't find.  
 
So I've muted every track in the project, including hidden tracks. I've bypassed all audio effects. This phantom audio is still playing. The audio tracks all output to a bus used for vocals. The only way to make the phantom audio go away is to mute the bus itself. 
 
How do I find the source of the phantom audio?

As mentioned in my post, "So I've muted every track in the project, including hidden tracks."

Are you using Aux Tracks by any chance? just curious cus I sometimes get audio bleed when using Aux tracks, mainly as buses. Similar thread here http://forum.cakewalk.com...n-Tracks-m3687247.aspx to which I replied a little while ago.