Years ago I worked for a small graphic design firm - maybe 6 people max...........

the wife of the owner used to come in every day - go directly to the fridge, rummage around - open up everyone's lunch and then just eat what she liked.

People started bringing in their own coolers to store their food - to keep her out - and they would leave them in their cars so she couldn't get to them. They used those frozen ice packs to keep things fresh.