Two cents from someone who works with HR folks. Label the jar clearly, with your name, a request not to use it without your permission, and a warning that the contents are very hot - RESIST the temptation to be deceptive in your labeling. While the goal would be to "get" those who are using it without your permission, rubbing the jar or lid with a pepper should be avoided, as it would also "get" someone who was just innocently moving the jar over, which is not your intent and would be considered an offensive move on your part. (ie - you don't want to hurt someone whose job is to clean out the fridge, for example.) After that, anyone who takes without your permission is inviting pain on themselves - not your problem. Use the hottest sauce possible for an extended period - you want a clear message sent to those who ignore your request, and word will get around. Some will take that word as a challenge, which is why you want to keep extreme heat for a while. After a handful of weeks though, you should be able to return to milder fare, if you wish.
. Would that be wrong of me??? 
well same thing happen to me. i had some super hot pepper powder in my cupboard. i was on holiday when my housemate decided to use some of my powder in their cooking. haha.. when i got back, they ask me what powder did i keep in the pepper powder container. they sort of used a few teaspoon full as they were thinking it was not hot. they told me they had sweat coming out from the head where they never taught it could hahah had burns in the mouth , burning urine and finally back orifice burns!!! it was a slow effect so they manage to eat half.! with cold beer! hehehehe.. i think they would ask me first before taking any of my things.
