Interesting...zanz "fixed" Fahrenheit by making the damage indicated on the card text become one with its original damage so as to avoid Fahrenheit still doing damage while frozen, delayed, etc. Now, I think this is the reason this occurred here. FQ has 68
based on that screenshot, so she would have had more than enough quanta to exceed that -5 you inflicted by Antimatter to make the overall damage inflicted positive and not negative. And since Permafrost only fails to affect creatures with negative attack, it proceeded through as normal. Interesting, though I'm honestly not sure if this can be considered a bug.