LadyClaire, that's terrible, and for her to lie about it knowing someone saw her, the mind boggles!
From the responses I think all of us here on this thread could give a few lessons on how to manage the communal fridge.
Well for my situation, I ended up deciding to remove my note. I had to go back in on the weekend so I re-read it and while it wasn't terrible or anything I just decided to take it down. One of the reasons was because that was my last week in that area so I wouldn't be there to do anything much to try to prevent it happening again. I did email one of the bosses to let her know what happened and I made a couple of suggestions, like the email notification for example. She replied in acknowledgement but was non committal so I don't know if anything will happen, though I'm sure if others complain they will make some changes.
Another reason I decided to let it go and put it out of my mind was because I didn't want a negative experience to cloud what otherwise was a good experience working in that area. If that makes any sense.
For those interested in what my scribbles on the notice said it was "No notice!!!" and "You threw away my lunch from TODAY", and under the deadline time I wrote "how were we supposed to know, no warning" . Nothing too terrible about that, but admittedly a little tantrum-like
and definitely not polite!