I accidentally created the ice cave of Hoth

So I went to the fridge in the garage containing a corny of double ipa and one of seltzer. Upon seeing the seltzer line frozen(very chilly last couple days) I removed it and brought it inside to thaw and turned the fridge temp down a bit (and of course filled a pint of beer). Fast forward to half hour later when I return to the garage fridge and notice some water on the floor. I open the fridge and am greeted with an admittedly pretty ice cavern which apparently spewed from the liquid post of the seltzer keg which had the gas still attached. Luckily I only lost a couple gallons of water and some co2. I can only assume the poppit was frozen during all this. Long narrative short...should I replace the poppit? And short of bringing the fridge inside is there any way this can be avoided in the future?

How is the temperature on your fridge being controlled? If you use a two stage controller, you can add a small heating element (light bulb even would be enough) to keep the temperature inside the fridge at your desired temperature. Converting electricity into warmth is much easier than converting electricity into cold.

As for the poppet, it's tough to say without seeing it. I can imagine that the freezing simply hoisted the valve open, but it's also possible that there was some more substantial damage. Test it out...if it still holds pressure, I'd wager it's fine.