Bad Day
OMG!! I'm so sorry that has been happening to you. I know how horrible it is to deal with.
Back when I worked (quit when I had surgery ) I had the same thing happen to me frequently. I finally had to start labeling my lunch in HUGE letters with my name and DO NOT EAT on everything I took in. When that didn't work, I started taking my lunch every day in an insulated lunch box. Finally, I was able to eat lunch every day without fear.
Hope you are able to find a solution that works for you!
Susan