Since it is concentrated, even if any yeast made it through the freezing process (which I doubt), the alcohol content should be way to high to allow any further fermentation. I'd say you should be fine.
I think most champagne yeasts can only handle up to about 18% ABV, some maybe a bit more, and about 20% for turbo yeast. Since you have concentrated alcohol there, you should be well above the 20% maximum that mere mortal yeast can handle. (If you have some sort of demi-god yeast, you might be in trouble)