If you're doing something you think is important ("other totally unpredictable thing (often support related)") at work and your boss says they think it isn't important ("The higher-up was 100% sure it wasn't a real problem and assumed I was exaggerating the situation.") then I would assume your boss is right and you are wrong and act accordingly (start ignoring or delaying dealing with these support-related things when you are busy with the "higher priority" work). Either it will turn out your boss was right and it won't be a big deal, or it will turn out your boss was wrong, and it will be clear to everyone, and before you know it a big pronouncement will come down from up high saying that that "unimportant" thing actually is very important.