get a copy of something from the hospittal and state your case. most people with these types of excuses never back them up and therefor loose there job due to it. take a doctors note or what not with you and explane it to them. dont give them a chance to dispute the case, you are a minor and your legal guardian had a medical emergancy. like I said take them the note dont let them ask for it. it looks more resoncable.
with the economic times the way they are, I am sure there is someone waiting to fill your position, so dont give them a chance. you have a legit excuse.