You can flash using pins beneath battery (aka serial). In fact, amongst them are USB D+/D- pins, You can use them to do cold reflash. Search, there are few topics here with pictures showing which pins are for what.

CAUTION! D+/D- pins beneath battery are connected *directly* to chip, without any protection circuit (as opposed to normal USB port). It means that You need to proceed with HIGH caution - any static, shortcut and whatsnot will go *directly* to chip.

For using as emergency flashing solution, You should be ok - but, for example, using this pins to make do-it-yourself general purpose usb port (as replacement for broken one), isn't great idea, probably.