Well, this was unexpected. The picture above is just over 33 hours after my previous post. It's a little early for me to trust it, since this is after the first feeding. I'll keep feeding it until it gives a consistent rise, but this is a great sign! It's smelling deliciously sour.
Here's what it looked like before the feeding (the morning after my post, T+17hrs):
And then here's the top-down shot about 16 hours later:
Nearly a full doubling, vigorous gas production. Just incredible.
Maybe it's a mistake, but I'll keep feeding it and posting the results.
You might get even better results by putting it in the jar instead of throwing it out there.