check the rim to see if you have dinged it and flattened part of the lip that grips the tire. If not you are probably right about he tire bead being worn. Either way the tire slipped of the rim and the tube ripped from the escaping air. Only other though is if you recently replaced a tube you might have pinched the tube between the rim and tire. Then it finally slid off when you jacked up the pressure.
Always place a the label at the stem and you can check placement easier.
There are several discussions here on blowing tires in a hot car at high pressure. The science seems to indicate it is a none factor. Hence the heat is not an issue.
Unfortunately you did not get the thrill of the explosive slip that some times occurs with a bang.
Eric