Sounds as though your starter motor switch would not switch off. Your starter motor kept going and burnt itself out. All the others are not that daft you know. As its an auto box you have a problem to get it going again without a new starter motor.
Thats good news. Keep an eye on the ignition switch though. I prefer to replace em myself but as long as you are aware of what caused it last time and what it felt like then you should be able to tell if it's getting back to the same sticky condition.