Perhaps like my case either he had a long timeout or it was turned on before the standby timed out. I often leave the volume up loud when turning the car off. This accounts for the rapid battery drain & when the voltage falls below a specific level the amp turns into a dirty power injector making the speakers sound as if they are over driven (which they actually are for the voltage supplied) much the same as if it was on AC being over-driven. Tweeters blow out quicker because the higher freq. gets hotter faster, more energy, the coils actually melt into one single blob. If I had a digital camera I would post the pics.
I believe this just another method that can occur that ends w/the same result, not a mistaken diagnosis. There are 2 different problems one being admittedly more rare than the other, I wouldn't dismiss it as being only the AC switches fault. Unfortunately you can't easily reproduce the IR problem w/o removing the AC from the equation & waiting for it to happen again, which is what I'm doing now or I could blast the IR detector w/random sunburst to get a close version of sun IR since the sun has the whole spectrum of IR it is easier. My player should never boot to AC, in the car now as long as Hijack does it's job. So if it happens again I'll know for sure. I'm also planning on removing the AC switch completely from the equation by physically bypassing it altogether.