Ah, many thanks!
Sorry, I totally forgot to mention it was from a 2012 Impreza.
So, I wasn't sure if it was a battery from 2011 (the '11D') or whether the battery was from 2013, (since there's a '13') which would make sense since it was purchased certified pre owned from a dealer in 2013. I thought maybe they had replaced it (and that maybe the dealers used the same batteries as factory, since it seemed these Panasonics were common for new Subarus).
It got a death knell from a dome light left on. It's not quite as cold here in Chicago as it is for you guys up north but not something I want to be messing around with on a cold winter night. I had tried to charge it with a 20 minute drive, and it was able to start up again, but then after sitting for ~3 days, it wouldn't start. I was thinking if it was from 2013, I'd give it a slow charge to try to restore it, but if it's from 2011 it looks like it's time for a new one.