Do I have a right to be upset with a co-worker who threw my food in the garbage?

No, you shouldn't be mad because you were given ample warning. BUT, a great solution that we used in my large office was this: every week on Friday at 3pm the fridge was cleaned out and a warning email/reminder was sent. Those of us who had items in the fridge, such as salad dressing, who didn't want it thrown out put labels on ours such as "WILSON FEB 8, 2008" so they would know that it was to stay in the fridge, we were aware it was in the fridge and had recently checked our items. As long as there was a recent label (most just taped a post-it on) then they didn't throw it out. Perhaps you could ask if that would be okay for some of the more long term items or items you've brought to eat the next day.