Main battery discharge means car can not start

I have posted a variant on this in the Yahoo toyota-prius group. The latest message in the thread is numbered 111544.

Here's what happened: A couple of weeks ago I was driving my 2001 Prius (about 70K miles) in Wilkes-Barre, PA. After parking the car for about an hour, I started it and got several of the warning messages on the screen. I tried to drive it, and a few blocks later it lost power and came to a stop. The main battery problem symbol remained on the screen. All attempts to start it, including jumping the 12V battery, failed. I had the car towed to Wilkes-Barre Toyota (large dealership, good interactions with the service department) who determined that the main battery had somehow become discharged. Their service report states "Hybrid control system has a code P3000 Hybrid Battery Control Malfunction with 2 info codes. INFO2 CODE 389 and INFO3 CODE 388." Does anyone know what these mean?

Wilkes-Barre Toyota got their hands on a main battery charger (apparently there are not that many, since they are expensive and not needed very often) and recharged my battery. All codes disappeared and I was able to pick up the car and drive it 300 miles today.

It is clear why the car wouldn't start. Without the main battery, you can not operate electric motors. Moreover, the electric motors are also the starter motors for the ICE, so this is a full catastrophic failure mode. Has Toyota or anyone else addressed the issue that this failure can not be corrected without very specialized equipment? Has this been addressed in more recent models? I have not seen any other reports of this--is it really that rare?

The only thing I can think of that may have caused this was that I drove on some very steep roads in the area the day the problem occurred. That could have caused successive deep discharge and recharge of the battery, and perhaps the computer detected something unusual and cut off charging to protect the battery. However, there was no warning.

Thanks for any insight.