Lyn, I'm almost sure they will come back. I read some article where they cut "turkey neck" heuchera to the ground and they come back beautiful. The deer just did this for you. I'm sure you are really sad about this because you have put so much work in your gardens.
Have you ever thought of gathering seed from your heuchera and winter sow them? I did that and came up with some nice garden plants. Maybe I told you already?