No hot water

It's possible that you are just not seeing what you would expect when looking at the hot out of the water heater. You may be looking at a hollow tube going into the tank. That is because when the check valve comes apart the insides get pushed into the water line. Look into the hot line that attaches to the hot out of the water heater. The insides of the check valve will fit inside that line until it comes to an elbow or other restriction. At that point it becomes a plug. If you can't see the pieces you should be able to test my theory by having somebody turn on the water pump and seeing water come out of the water heater. If you have water there, you will need to find the insides of your check valve downstream. I was lucky. I have a 90 degree elbow about 3 inches from the water heater.