Hopefully the plug just popped out when it froze. Replace the plug and see. If the tank is damaged, it's new water heater time.
I have heard of self draining water heaters but have never seen one. I think you were given some bad info by the tech. Go to the Atwood site and read the manual for the proper way to drain it.
Get a couple of spare plugs as they do cross thread and they are cheap.
Atwood does not recommend installing a anode rod.
2011 351RLTS Eagle, Mor/Ryde suspension & pin box
06 F350 Lariat PSD, SRW, LB, CC, EGR delete kit, 16K DrawTite hitch, Timbrens, TST TPMS
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