I had a similar thing happen to me last week -- left the dome light on last weekend and killed the battery. What I don't understand is why that should have affected the State of Charge of the main battery pack at all -- from what I understood the connection to the main pack was severed when the ignition was out. Also, if it really were discharging the HV battery using the voltage converter, there's no way a dome light could have gone through that much power in a day or so. I don't think this actually happens though (actually, the last time I needed to get jumped about a year ago, the HV battery still indicated a full SoC)

Anyway, it force-charged for a minute while I drove up the backside of the hill I live on, then I had a huge downhill stretch to charge the battery. What happened is that while I was charging on the way down it jumped rapidly from about 1/2 charge to just short of full charge. That distance of that "jump" is about the amount of charge I usually have left in the pack at home, so I think the computer just didn't "catch on" to how much power was really in the pack when it indicated no bars.

However, the good news is that the car is driving much better now than it has been the last few weeks. I kept having the feeling like the system was doing heavy charging all the time before, as shifting into neutral would relieve a substantial amount of load even at very slow speed coasting (like having A/C compressor on all the time). That's not the case anymore. It seems I'm getting more assist from less charging out of the battery, so the little unintended recalibration of the pack seemed to have helped out a lot.

What I experienced though seems to imply that the Hybrid Pack didn't actually get discharged, as after a couple minutes of charging, the indicator on the dash basically said "oh crap, this is full not half empty" and cut out charging, I didn't actually lose the 1/2 SoC I had when I left my light on, the computer just lost track of it for a while.

Also, my experience the weeks before seems to imply that the system was never letting the battery pack charge all the way up when it had the opportunity, or perhas that the display was out of sync with the real SoC, so it was simply leaving a lot of my battery actual capacity unused. That would explain why there was more parasitic charging, and less sustained stretches of assist.

However, this experience is making me think it might be a good idea to drop in a larger capacity 12v battery, or even wire another smaller one in in parallel to the system so the 12v system won't go dead so easily.