Hi Charlie,
Ain't that pomegranate supposed to be hardy down to Zone6 ?
If so I would suppose that it can handle -20°c with no problem ... Perhaps because it is potted or young , it doesn't resist for now .
I'm starting to look at something else to add to the garden, and I'm still hesitating between a pom or a kaky or ...
A neighbor had a kaky that froze down below the graft junction in 2012, so that scalded me for now - the tree is still alive ... well the rootstock that is...
But if I can find something cold hardy in the wild in Zone7, I might give it a try ... someday .
I still haven't seen poms being sold here ... in my Zone7 .