If it was not frozen solid the yeast should be fine. I'd make another starter with it just to be sure though.
For future reference, if it was frozen solid you'll probably get 99+% die off, but then with billions of cells there will probably be enough to revive if it is a hard to find strain. If not, just replace it.
To prevent it in the future, put it in a warm spot in the fridge - top shelf, close to or on the door. You might have had it right next to or under the cold air vent from the freezer.