The problem with this is that you have no other recourse. Taking it to HR would result in you being called a little bitch and to suck it up. Taking it to court would be thrown out as frivolous. Video evidence would involve a bit too much effort if the thief was halfway cautious and you might get in trouble for unapproved filming in a workplace or some bullshit like that.
What if by chance it's someone who is just hungry and couldn't afford to feed themselves at work? I know it's not probable, but I've seen it before at a place I worked. (you would have never guessed the guy couldn't) I'm just stating a hypothetical in this case, but what if? Then you cost someone their job that spends each dime they make on their family or a sick daughter or something equally important?
^ you said it, guest but i really feel the need to say it again: if you can't fuckign afford food, ask for it. I'm terribly strict when it comes to sharing my food but even I'd definitelly say yes. There's no shame in asking for something as necessary as food. But if you steal it, well.
All you would need to do is send that note to HR and that person would be fired. She admits to bringing drugs into work and dosing a coworker... Theyre freaking brownies. Get over it.
In that case, checkmate indeed.