Yeah, I'd say the first thing to do would be stop replenishing the candy drawer yourself and put out a big ole jar with a sign that says "DONATIONS FOR CANDY JAR." Then I'd get a lockable container for my own personal stuff if it seemed like people stealing my food was going to be a problem. However, I wouldn't set it out prominently (because then it might seem belligerient), but find somewhere discreet for it.
Also, you have to realize that if it was a big bag of sunflower seeds left out in the open, it's immediately going to be tagged as public food. This was true on my hall at boarding school, as well as in the break room of the busy hospital lab where I once worked. If I can see it, I can eat it, and if I'm an asshole, I'll eat it even if it's got your name on it. Chaulk it up to expierence and your boss just not thinking about it, and keep stuff hidden from now on
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Sage knows our mythic history, King Arthur's and Sir Caradoc's
She answers hard acrostics, has a pretty taste for paradox
She quotes in elegiacs all the crimes of Heliogabalus
In conics she can floor peculiarities parabolous
-C'hi