Toyota Highlander excess heat safety problems

A recent incident with my 2008 Toyota Hybrid Highlander raises major safety concerns in my mind. I wonder whether Toyota is taking steps to avert such problems in the future, and whether other drivers have experienced anything similar.
Last week, I parked the Highlander in my garage, believing that I had pushed the power button, thus turning off the vehicle. I do not recall hearing the typical warning beep that occurs when leaving the car with the power on. My remote key was removed with me and did not remain anywhere near the vehicle. Nonetheless, on my return to the garage approximately twelve hours later, I found the temperature to be in excess of one hundred degrees, the car surface itself painfully hot, and the inside of the car akin to a sauna bath. Some cd’s in the glove compartment were too hot to touch. There was a noxious smell apparently emanating from the overheated battery pack. The “no key present” light was flashing, the fan was blowing very hot air, and the dash lights were all on. Fearing a fire, I tried to start the car to move it away from the garage, but it would not start. Pushing the power button several times, I was able to shut down all systems, and I opened the car and garage doors to let it all cool down. I had it towed to the dealership.
There seemed to be no description in my web research that indicated this could be a common problem. This model evidently has a nickel-metal-hydride battery pack, not known to cause “thermal runaway,” which is what my situation seemed to be. Although there was the suggestion that the new lithium-ion battery pack anticipated for the upcoming plug-in hybrids could experience it.
At any rate, two days of observation, research, and a battery charge in the dealership shop resulted in the following explanation: They determined that I must have left the power on after all, and that the vehicle is not programmed to shut down after any period of time in which the key is not present. Furthermore, I was told that the battery pack actually vents heat into the vehicle, under the back seat, and the vents were blocked by two bags of newspapers and a blanket. So, with the battery pack active, and the vents blocked, there was an automatic call for the fans to come on to circulate the air. That in turn ran down the battery to the point where it would not start but allowed the fans to keep blowing hotter and hotter air. In acquiring the vehicle, I was never warned or cautioned about either circumstance.
Conclusion: A. NEVER leave the vehicle without shutting down the power and confirming it by the appropriate sound signal, because it won’t ever shut down automatically. B. NEVER allow anything on the floor behind the front seats to block the vents under the back seat, thus allowing the battery pack to overheat dangerously.
Since I suspect that most drivers can be as absent-minded as I can, I believe the current design of the vehicle is inherently dangerous, and in the event of a fire or an explosion from excess heat, could cause loss of life and property. I believe Toyota should immediately warn drivers of these conditions. And better yet, I believe Toyota should make design changes to permit an alternate venting outlet for the battery pack, and incorporate a timing system so that the vehicle can not remain powered indefinitely without a key in the immediate vicinity.