Am I right to get offended by this?
No. Presumably, you are an adult who knows how to take care of yourself. If you are feeling sick, you should leave and go home, or go to your room, or go to the hospital... or you should ASK for help if you need it. If you just sat there, you can't blame them for not taking you seriously. You can't expect them to read your mind.
Mean Jelly Bean
What did you want them to do? Throw you a pity party?
You have two arms, two legs, a mouth and a brain and still can't figure out what to do? Excuse yourself and go to the restroom or go home. If you feel you need their help, ask for it.