Battery dies within minutes

On 2 occasions now my 08 Prius battery has died mysteriously and quickly. The circumstances were similar both times.

I'd been driving in a parking lot for a while searching for a space. Then parked for about 15 minutes. Then started the car, but decided instead I needed to make a phone call. Maybe started the call while it was still running, but then turned car off (don't remember for sure). It was hot & the call was taking a while, so I rolled down the windows half way on driver & passenger sides. Then opened driver door for more air flow. After about ten minutes, I go to the start the car and it's DEAD! Both times had to call AAA to get a jump.

After the first incidence I took it to Toyota dealer to check the battery, they said it was fine. Is there some bad combination of open door (light on), headlights on, bluetooth, proximity key & an ipod cable (just the cable) plugged into console that could cause the battery to drain in ten minutes???