Why don't I have hot water after shutting off the water supply for a while?
On the upper thermostat, there is a sensor that would trip if the water got too hot inside of the tank, BEFORE the TP valve would blow off (which we assume didn't happen because you didn't mention it). It's called an Energy Cut Off (ECO) switch. There is a red button on it. Open the upper access panel, you should see it there. Push the red button and if you hear it "click", it was tripped and it should work again after that. If not, or it doesn't click, it's something else. If it trips again really soon after resetting, an element was damaged.

And it's 240V, but it is 6,000 watts...