It doesn't sound like your manager didn't get your message, in which case they're being a dick. If they got it and wanted you to report it another way, the thing to do as a manager would be to say that you need to do something, not ignore it.

Only thin I'd add is about your email. You're 17, it's not like you have a busy social email scene, Surely the only people emailing you are work, school, and companies sending you promo emails. No need to delete anything, just throw it into folders (either automatically, or as it comes in) and let it stay there forever. Then, if you do accidentally misjudge something, you can find it later instead of it being gone forever.