Hey, Im in zone 9, and the same exact thing happened to mine. It was that cold we had for a couple of days in january i believe. It hit like 32 or something for 2 days. That did it for me. I cut it down to about 10 inches, but there is no green or new growth on it. Im getting a little worried that perhaps the cold killed it. I was at a few nurseries and saw that they were putting out growth everywhere. I have the Harlequin Davidii species. I am anxiously waiting for it to grow 'somewhing' for a few weeks, if not i might just replace it.
Q