There is something not correct in your information. The IGFA record for Pacific sailfish on a fly is only 136 pounds. Even the all time all tackle record sail is only 221 pounds. Therefore, either your weight or your species is incorrect. With care it is quite possible to catch large fish on relatively light tippets. Doing so is somewhat controversial because it either requires having the fish on for a very long time which increases the chance that you will kill it, or it requires the captain to back down on the fish very quickly, for the leader butt to touch the rodtip (therefore supposedly making it an official catch) and then either trying to get the fish to throw the hook or breaking it off. Since I don't have cable I wasn't able to see the program you're referring to so I don't know which way they went with this fish. By the way, twelve pound really isn't too bad. A good fisherman can land a sailfish of normal size in a reasonable time with high quality twelve pound class tippet material. The real circus is when they start using two, four, and six pound class.
Is it possible the fish they caught was a marlin? A 250 pound striped marlin on twelve pound class is about the same as a 100 pound sail on four or six pound. Marlin are so tough to get on the fly and have so much more endurance than a sailfish, that almost everyone uses at least a twenty pound class when pursuing them. The truth is that some guys say to heck with the IGFA or a possible record and use thirty pound or more. I'd be curious to know if you think you had the weight or the species incorrect.