huge poolcrete crack while drying now PB is putting liner in?

Our new vinyl pool is being installed and they did the poolcrete two days ago. They covered the pool opening with a big tarp and told me to run a heater they had left to help prevent the concrete from freezing. (Days are in the 50's, nights are in the 30's) When I looked at it yesterday after they removed the tarp, there is a long gash of missing poolcrete in the deep end where the sides meet on the slope. It looks like a big strip (about 4 inches wide and at least 4 feet long is missing and I can see dirt) PB said that happens all the time and he will patch it and still plans to drop the liner today while it is wet. I'm nervous that the replacement area may not hold or set up correctly and then we'll have a mess where the liner covers that area. Help!