On my 1996 Discovery, I replaced my hot water heater a few years ago and found during the R&R process a couple of places where the "hot rod" or electric portion could lose electrical continuity.
First, there's no telling where the installer placed the main fuse for the unit. It could be in line, or they could have come off the panel where the 120-volt breakers are. Sometimes they use a solid connection and sometimes they just use a "slip-on" connector that could come loose.
Depending on the manufacturer of the electrical portion, there could be a fuse on the control box for the unit itself. You should find that sitting directly on top of the water box of the hot water heater. It may or may not be covered with insulation. Mine was glued right to the top of the water tank of the water heater.
At any rate, you should be able to pull out some drawers or open some cabinets to see most of the wiring for the heating element. I'd be willing to bet one of them came loose or a hidden fuse blew on you. Of course, if it is a blown fuse, that could very well be caused by a bad heater element. It would be worth pulling the element out to look it over. I soaked mine in vinegar for a day or two and it cleaned up just fine.
Good luck finding your problem. No doubt others here will have better suggestions for you.