I'm assuming something happened to your rock? If so, what happened? That would be an easier question to answer.
Usually if the rock is still in salt water (say between 1.015 and 1.040) it is likely to have some sort of life still on it. Heck, I had a Coral Banded Shrimp live in a sesspool of a 10g tank for 6 months (no waterchanges, no water topoffs) before I knew he was in there! I thought he died when the heater stuck on and cooked the tank at 98 degrees. The tank had no heater anymore, and was only half full due to evaporation, so who knows what the salinity was at!
However, if there is significant die-off on the rock, it would be REALLY unwise to use the rock without "cooking" it (doesn't involve a stove...ask if you don't know) for several weeks/months until the phosphates reached 0.