If your Lithodora has some green leaves, its alive. If it has no leaves or brown leaves only, it may be dead. Check that with a "scratch test": scratch the stems with your fingernail. Green below the surface means the branch is alive, brown or hard as a rock means dead. Check in several places as part of the plant may be dead and part may be alive.
If you find signs of life, care for it as usual and wait for new leaves.