Lucky water heater fix

So we get to our camp site and get everything setup. Hook up the electricity and water and I see some water coming out of the water heater vent. I tell the wife "water heater is leaking". About that time she sees a flood inside! I turn it off and start investigating. I see a fitting spewing out water. Probably froze on the one night we had cold below freezing here in SC.

Anyway, I unscrew the pipe and I think "if I only had a plug". Lo and behold the drain plug is the same size! Get it screwed in and no leak!