How to get away with not eating and how to hide purging?

I'm on a diet and yesterday when I was with my friends at the mall and they wanted food at the food court, I said I wasn't hungry but one of them nagged me and said "you need to eat", no I don't I'm a fat cow. So I ate a 6 inch sub from Subway (500 calories I know a bunch) and chugged a bottle of water, then 20 min later I went to the bathroom and threw up, I popped some gum in my mouth to hide bad breath but my eyes were red and my finger has teeth marks, what do I do to hide these symptoms?
How to get away with not eating and how to hide purging?
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