i would not move your rock mate you sure its dead anyway have a good look round when lights go off but if it is dead in tank bet crabs n snails would of seen it off by now mate
all the best shaun
i have wedged em upright with rocks before i would put the half not stuck to anything on a rock it will stick on it in time not sure if glue would work but why not i would try it what you got to loose
let us know if it works
shaun