"I felt that if they were willing to pass due to me obviously locking up on a Skype + Google-Doc shared whiteboard, and on the most basic of JavaScript skills (which were clearly elaborated upon within the project)"
Or it could be a simple miscommunication, or they thought somebody else done the app given your performance on the interview. Reaching out and asking will cost you little compared to potential windfall.
Exactly. I mean, it would take a fairly skeptical person to think that you submitted someone else's code but maybe they just weren't willing to take the risk.
Either way, I think you've nothing to lose by sending that mail/picking up the phone. Regardless of the doubts the interviewer may have in you post-interview they'll know that everybody is prone to a bad day every once in a while.
Or it could be a simple miscommunication, or they thought somebody else done the app given your performance on the interview. Reaching out and asking will cost you little compared to potential windfall.