Send it back to Ruger.
The firing pin bushing is threaded and has a locking nut on the hammer side. The gun store knocking the bushing back does nothing and it will move forward again then tie the gun up as the cylinder rotates. This isn't a might happen, it is a will happen.
Dry firing a gun like a LCR does nothing, use it as is and it will be fine. The yellow plastic disc is a safety disc to show the fire arm isn't loaded.