There's no prize once you catch up to bapu, Colin! That's why I dropped out of the competition.
As for the phantom notes, we can start with the assumption that the sampler isn't just making sound on its own, that it is being instructed to make sound somewhere. I can think of a few possible explanations.
I'd start by muting the MIDI track that's driving the synth/sampler. If the notes go away, then there is some MIDI data lurking in there and you may need to refer to the event list to find it. If the notes persist, then they're coming from another track, in which case it's probably a routing issue. Keep muting MIDI tracks until they cease.
If you've muted every MIDI track and still hear the notes, then you are indeed in the twilight zone. Especially if you discover that your computer is unplugged and your home was built atop an ancient burial ground.