Thanks for your replies!
When I got home (after stopping to buy a frozen meal, still fuming), I sent a text to my friend telling her what happened. She said she laughed, which gave me some perspective and yes, it's not the end of the world, but it was the last straw after a long week.
What really got me what the total lack of common sense, I was often the (unappointed) kitchen and fridge cleaner at my previous job, and I was always very careful about it. An email and a notice was posted on a Monday, stating what was to happen on a Friday, and even then discretion was used about what was thrown out. And containers were not thrown away, unless they were clearly disposable take-away ones, as some people do.
Can I share a tip I learned - for very rotten food that you don't want to open but don't want to throw the container, freeze it overnight and at the end of the day toss the frozen rotten block out and put the container in the dishwasher!
I guess I was also a little cranky at myself because, even though there is no policy, I would often stick a note on my food with my name and the date and this time I didn't. So I don't forget food that I'm taking home (like lunch time shopping), I stick a note on my handbag.
Thanks for all of the good suggestions, lots of great ideas and I will pass those along. I like the idea of putting the sticky notes and markers next to fridge so people can label their items.
Still haven't decided what to do, I will have another look with fresh eyes today.
I will have to check out PassiveAgressiveNotes site, I didn't know it existed, definitely sounds like mine fits there