The lower thermostat is usually next to the drain valve and you've probably shorted its output and fried its solid state relay inside (need a new thermostat).
But, Tom: DID YOU NOT SWITCH THE POWER OFF BEFORE DRAINING YOUR WATER HEATER?! Â The thermostat is normally covered to prevent an accident like that but regardless, you are absolutely not supposed to do any work on the heater, least of all draining the water out of it, before switching the power off at the breaker. A number of very nasty accidents could have resulted, including electrocution, and it could have (and perhaps already have) lead to damage to the heating elements. They cannot be energized without the water to cool them, they just burn up.
If it was your lucky day, you probably need only a new thermostat.
Stay safe.