LR can probably be out of water for a few hours with only minimal die off as long as it's kept moist. A good trick is to wrap the LR in saltwater-soaked newspaper.
For what it's worth, I just moved all of the livestock and LR out of my 65 this past weekend and into a temporary tank a little more than an hour away using the newspaper method. In total, the rock was out of water for about 2 hours and I had no noticible die off, including some zoanthids scattered around the rocks.