Live Rock, cold water and dead bristle worms oh my.

[Blue Spot Octopus]

I had to remove half of my live rock, I put it in a trash can with a power head and a heater. The problem came about when I had to remove the heater, Dumb idea, well the cold water killed the bristle worms and fouled the water. I put he live rock/maybe dead now back in the tank. I dumped all of the water.
Question is my tank going to have to go through another cycle? The rock has been in the tank for over 15 years.

Thanks in advance

 

[Shibaken3]

bacteria should still be on the rock. so its still alive

 

[Blue Spot Octopus]

Thanks, I noticed the live rock looks like what is in the tank already, so I am glad it did not have a die off.