New Dupe in Sythe?

People run across them accidentally... Some of them sell their methods after using it for themselves. Some leak the method in forums and stuff. That's how JaGex gets to know about them and patches them.

Dupes usually get patched within a few hours of discovery, because some bitches can't keep their mouths shut. So yes, it'll take a great deal of luck to run into one yourself, or to be able to purchase a duping method before they get patched.

 

So the game thinks you died, but you didn't