Well water is funny thing with electronics, really.

The technology today is such that even a small amount of moisture in the wrong place WILL KILL your device, with a reasonable odds.

How it works; when water or moisture gets into the device there will always be small current running thru the damp surfaces, between PCB tracks close to each other, unless the water is distilled and absolutely pure. (and that wont ever be the case since as you have used & held the device in your hand there is always small amount of salts&stuff on the device itself)

The tracks on the PCB are so close to each other and so thin that even the minuscule current caused by the damp surfaces will electrocorrode something in few hours. AND this action will continue even when you switch the device off, as long as the battery is present in the device.

The only way to fix this, is to immediately open the device and remove the battery before trying to dry the device up any way.