Welcome to the forum. People get a little pumped up when they see a gun with a missing serial number. Personally it isn't a big thing with me. I have been around guns for over 50 years, transporting, hunting, shooting at ranges and in leagues on teams. Not once in all of those years have I ever been stopped and had one of my guns examined. I would probably take the gun to a gun smith and have him stamp the cylinder number on the butt.
Even if the gun was used in some nefarious way 22 years ago, probably nobody cares today.