I'm hoping that SE is banning people who use the Teleport Hack, but are not relying on player reports to corner those guilty.
I was camping Lizzy recently, and saw another camper who would 'warp' about twenty feet and then stop. I figured it was lag, and since neither of us got claim on Lizzy, so I'm guessing it was. That, or the person was able to warp, just not good at it. Just remember that not everyone has a fast connection, lag happens, and it IS possible for someone to outclaim you without using hacks. Some times the server pays more attention to the worm who just dug himself a new hole than a player who's walking around.
Also take note that Steal/Provoke/other Job Abilities take effect immediately. So if they saw JEJ pop and had been spamming a /ja Provoke <stnpc> macro, chances are that they'll have the claim before your eyes register the color of the name.
Thank you for not posting names, as I'm sure you know this is a community-based game and reputation is very important.
In the future, good luck on JEJ and other Notorious Monsters. Luck plays a heavy factor in this game, and a newbie who has a monster right in front of them has a better chance of claiming than a self-proclaimed master who needs to take a step or two to get into claiming range.
/salute