Wife turned the wrong switch ON (gas) and it lit......BUT it went out or you had wife turn it off BUT it won't relight......Correct????
Do you have 2 switches on panel where light is?
Just one switch?
Is there another switch in outside compartment??
Which Brand WH......Suburban or Atwood??
The electric and gas are two separate heating sources......turned ON & OFF by separate switches.
Just a guess.....you have a Suburban with an ON/OFF switch in outside compartment that is ON and electric element burnt out due to WH tank being drained and RV was plugged into AC power source.
No indication of electric working, being ON except for hot water when AC power is available.