I am super sad over the death of this tree. After the hard freeze we hard came a month-long period of warm weather and the tree started to push out lots of bud. Then came 2 nights of frost with temperature around 32 deg F, which I didn't think would be an issue. The frost killed all the young buds and the tree never recovered.
How do you know it's dead?
FWIW, I had a smaller live oak I brought up from Texas a while back. I overwintered it in the backyard for about five years. In that time, it lost every branch it grew the previous summer when it froze over the winter. It's roots were heavily mulched and weren't killed off. The plant sprouted new buds every spring.
I finally gave up on it because I couldn't get branching on it.
All that means the root mass (and probably significant portions of the top) on yours may still be alive. I wouldn't give up on it just yet.