After going through all of the weird stuff that's happened recently I found this:
I don't care what it means and I don't care how it got there. All I know is it'd take something pretty special to get that sound hidden on my recording; more than anyone I know could do. More than anyone could do without me noticing... So I'm just going to leave it. Maybe if I stop giving it attention whoever is doing this will get bored and go away.