Well, let's start with "no warning": There is a battery meter on the screen at all times unless you're using a WPS that explicitly removes it. So not knowing your battery status is as simple as "you didn't look at the screen to check it, ever".
100% unresponsive is pretty reasonable if the battery is *empty* as how will it have the power to respond if there's no juice in it? Your description even hinted at it not having enough power: It chunked (not enough power to spin up the disk) and rendered half the screen (not enough power to draw the whole LCD before running out again).
As for why plugging it in immediately didn't help? In many cases plugging it in starts the charging routine. The battery itself must reach a high enough voltage to boot the device. So if the battery is below that level, you must wait for it to charge up to that level before you can boot the device. In fact *many* rechargeable electronic devices work in a similar way: When the battery dies it must be charged for a certain amount of time (as little as several seconds to as much as an hour or more) before the device is usable at all.
I can understand why you were surprised, but it sounds to me that most of that is simply because you didn't apply much reasoning to the situation, and instead panicked and decided that your device might be bricked.
The real concern is your use of the word "brick" at all. By the time you posted the message, you already knew that your unit was not bricked. We really, REALLY do not like people throwing this word around lightly in these forums. A bricked player is by our definition irrecoverable without hardware work (opening the player and hooking up an external interface, or replacing a piece of internal hardware, in many cases). Pseudo would mean that it was acting like it was bricked, and your descriptions of its actions don't sound like it was even close to acting like it was bricked. We appreciate it if you try to avoid using words that can make other people more frightened of the software. We'll readily admit if something *is* bricked, but something acting in a perfectly logical way when its battery is dead isn't even close to bricking.